appendix b.1 the cartesian plane a25 333353 appb1 pg a25

The Cartesian PlaneJust as you can represent real numbers by points on a real number line, you canrepresent ordered pairs of real numbers by points in a plane called the rectan-gular coordinate system, or the Cartesian plane, after the French mathemati-cian René Descartes (1596–1650).

The Cartesian plane is formed by using two real number lines intersecting atright angles, as shown in Figure B.1. The horizontal real number line is usuallycalled the x-axis, and the vertical real number line is usually called the y-axis.The point of intersection of these two axes is the origin, and the two axes dividethe plane into four parts called quadrants.

Figure B.1 The Cartesian Plane Figure B.2 Ordered Pair

Each point in the plane corresponds to an ordered pair of realnumbers x and y, called coordinates of the point. The x-coordinate representsthe directed distance from the y-axis to the point, and the y-coordinate representsthe directed distance from the x-axis to the point, as shown in Figure B.2.

The notation denotes both a point in the plane and an open interval onthe real number line. The context will tell you which meaning is intended.

(x, y)

�x, y�

�x, y�

(x, y)

x

y Directed distance

Directed distance

(x, y)

x-axis

y-axis

−2 −1 21

1

2

−1

−2

(Verticalnumber line)

(Horizontalnumber line)

Quadrant I Quadrant II

Quadrant III Quadrant IV

Originx-axis

y-axis

Appendix B.1 The Cartesian Plane A25

Example 1 Plotting Points in the Cartesian Plane

Plot the points and

SolutionTo plot the point imagine a vertical line through on the x-axis and ahorizontal line through 2 on the y-axis. The intersection of these two lines is thepoint This point is one unit to the left of the y-axis and two units up fromthe x-axis. The other four points can be plotted in a similar way (see Figure B.3).

Now try Exercise 3.

��1, 2�.

�1��1, 2�,

��2, �3�.��1, 2�, �3, 4�, �0, 0�, �3, 0�,x

−3−4 −1−1

−2

−4

1 2 3 4

1

3

4(3, 4)

(3, 0)(0, 0)

y

(−2, −3)

(−1, 2)

Figure B.3

Directed distance from -axisy

Directed distance from -axisx

B.1 The Cartesian Plane

What you should learn� Plot points in the Cartesian plane and

sketch scatter plots.

� Use the Distance Formula to find the

distance between two points.

� Use the Midpoint Formula to find the

midpoint of a line segment.

� Find the equation of a circle

� Translate points in the plane.

Why you should learn itThe Cartesian plane can be used to represent

relationships between two variables. For

instance, Exercise 85 on page A35 shows how

to graphically represent the number of

recording artists inducted to the Rock and

Roll hall of Fame from 1986 to 2006.

Appendix B: Review of Graphs, Equations, and Inequalities

333353_APPB1_pg A25.qxp 5/6/08 3:00 PM Page A25

A26 Appendix B Review of Graphs, Equations, and Inequalities

The beauty of a rectangular coordinate system is that it enables you to seerelationships between two variables. It would be difficult to overestimate theimportance of Descartes’s introduction of coordinates to the plane. Today, hisideas are in common use in virtually every scientific and business-related field.

In the next example, data is represented graphically by points plotted on arectangular coordinate system. This type of graph is called a scatter plot.

Example 2 Sketching a Scatter Plot

The amounts A (in millions of dollars) spent on archery equipment in the UnitedStates from 1999 to 2004 are shown in the table, where t represents the year.Sketch a scatter plot of the data by hand. (Source: National Sporting GoodsAssociation)

SolutionBefore you sketch the scatter plot, it is helpful to represent each pair of values byan ordered pair as follows.

To sketch a scatter plot of the data shown in the table, first draw a vertical axis torepresent the amount (in millions of dollars) and a horizontal axis to represent theyear. Then plot the resulting points, as shown in Figure B.4. Note that the breakin the t-axis indicates that the numbers 0 through 1998 have been omitted.

Figure B.4

Now try Exercise 21.

�1999, 262�, �2000, 259�, �2001, 276�, �2002, 279�, �2003, 281�, �2004, 282�

�t, A�,

STUDY TIP

In Example 2, you could havelet represent the year1999. In that case, the horizontalaxis of the graph would not havebeen broken, and the tick markswould have been labeled 1through 6 (instead of 1999through 2004).

t � 1

Year, t Amount, A

1999 262

2000 259

2001 276

2002 279

2003 281

2004 282

333353_APPB1.qxp 1/22/07 8:32 AM Page A26


Figure B.5 Figure B.6

Some graphing utilities have a ZoomStat feature, as shown in Figure B.8. Thisfeature automatically selects an appropriate viewing window that displays allthe data in the list editor, as shown in Figure B.9.


The Distance FormulaRecall from the Pythagorean Theorem that, for a right triangle with hypotenuseof length c and sides of lengths a and b, you have as shown inFigure B.10. (The converse is also true. That is, if then the triangleis a right triangle.)

Suppose you want to determine the distance d between two points and in the plane. With these two points, a right triangle can be formed, asshown in Figure B.11. The length of the vertical side of the triangle is and the length of the horizontal side is By the Pythagorean Theorem,

This result is called the Distance Formula.

d � ��x2 � x1�2 � �y2 � y1�2.

d � ��x2 � x1�2 � �y2 � y1�2

d2 � �x2 � x1�2 � �y2 � y1�2

�x2 � x1�.�y2 � y1�,

�x2, y2��x1, y1�

a2 � b2 � c2,a2 � b2 � c2,

1998.5 2004.5255.09

285.91

The Distance Formula

The distance between the points and in the plane is

d � ��x2 � x1�2 � � y2 � y1�2.

�x2, y2��x1, y1�d

Figure B.7

d

x

y

(x2, y2)

(x1, y1)

(x1, y2)

⏐y2 − y1⏐

⏐x2 − x1⏐

x2x1

y2

y1

Figure B.11

a

b

c

a2 + b2 = c2

Figure B.10

1998 2005

300

0

You can use a graphing utility to graph the scatterplot in Example 2. First, enter the data into the graphing utility’s list editoras shown in Figure B.5. Then use the statistical plotting feature to set up thescatter plot, as shown in Figure B.6. Finally, display the scatter plot (use aviewing window in which and ), as shown inFigure B.7.

0 ≤ y ≤ 3001998 ≤ x ≤ 2005

TECHNOLOGY T I P

For instructions on how to use the list editor, see Appendix A;for specific keystrokes, go to thistextbook’s Online Study Center.

TECHNOLOGY SUPPORT

333353_APPB1.qxp 1/22/07 8:32 AM Page A27


Example 3 Finding a Distance

Find the distance between the points and �3, 4�.��2, 1�

Algebraic SolutionLet and Then apply theDistance Formula as follows.

Distance Formula

Simplify.

Simplify.

So, the distance between the points is about 5.83 units. You can use the Pythagorean Theorem to check that the

distance is correct.

Pythagorean Theorem

Substitute for

Distance checks. ✓


34 � 34

d. ��34 �2�?

32 � 52

d2 �?

32 � 52

� 5.83 � �34

� ��5�2 � �3�2

� ��3 � ��2��2 � �4 � 1�2

d � ��x2 � x1�2 � �y2 � y1�2

�x2, y2� � �3, 4�.�x1, y1� � ��2, 1�Graphical SolutionUse centimeter graph paper to plot the points

and Carefully sketch the linesegment from A to B. Then use a centimeter ruler tomeasure the length of the segment.

Figure B.12

The line segment measures about 5.8 centimeters, asshown in Figure B.12. So, the distance between thepoints is about 5.8 units.

1C m

23

45

6

B�3, 4�.A��2, 1�

Substitute for and y2.x1, y1, x2,

1 2 3 4 5 6 7

1

2

3

4

5

6

7 (5, 7)

(4, 0)

d1 d3

d2

= 50= 45

= 5(2, 1)

x

y

Figure B.13

The Midpoint FormulaTo find the midpoint of the line segment that joins two points in a coordinateplane, find the average values of the respective coordinates of the two endpointsusing the Midpoint Formula.

Example 4 Verifying a Right Triangle

Show that the points and are the vertices of a right triangle.

SolutionThe three points are plotted in Figure B.13. Using the Distance Formula, you canfind the lengths of the three sides as follows.

Because you can conclude that thetriangle must be a right triangle.


�d1�2 � �d2�2 � 45 � 5 � 50 � �d3�2,

d3 � ��5 � 4�2 � �7 � 0�2 � �1 � 49 � �50

d2 � ��4 � 2�2 � �0 � 1�2 � �4 � 1 � �5

d1 � ��5 � 2�2 � �7 � 1�2 � �9 � 36 � �45

�5, 7��2, 1�, �4, 0�,

333353_APPB1.qxp 1/22/07 8:32 AM Page A28


Example 5 Finding a Line Segment’s Midpoint

Find the midpoint of the line segment joining the points and

SolutionLet and

Midpoint Formula

Substitute for and

Simplify.

The midpoint of the line segment is as shown in Figure B.14.


�2, 0�,

� �2, 0�

y2.x1, y1, x2, � �5 � 9

2,

�3 � 3

2

Midpoint � x1 � x2

2,

y1 � y2

2 �x2, y2� � �9, 3�.�x1, y1� � ��5, �3�

�9, 3�.��5, �3�

Example 6 Estimating Annual Sales

Kraft Foods Inc. had annual sales of $29.71 billion in 2002 and $32.17 billion in2004. Without knowing any additional information, what would you estimate the2003 sales to have been? (Source: Kraft Foods Inc.)

SolutionOne solution to the problem is to assume that sales followed a linear pattern. Withthis assumption, you can estimate the 2003 sales by finding the midpoint of theline segment connecting the points and

So, you would estimate the 2003 sales to have been about $30.94 billion, asshown in Figure B.15. (The actual 2003 sales were $31.01 billion.)


� �2003, 30.94�

Midpoint � 2002 � 20042

, 29.71 � 32.17

2 �2004, 32.17�.�2002, 29.71�

3−3−6 6 9

−3

3

6

−6

(9, 3)

(2, 0)

Midpoint

x

y

(−5, −3)

Figure B.14

Year

Sale

s(i

n bi

llion

s of

dol

lars

)

29.0

29.5

30.0

30.5

31.0

31.5

32.0

32.5

2002 2003 2004

Kraft Foods Inc.Annual Sales

(2004, 32.17)

(2002, 29.71)

(2003, 30.94)Midpoint

Figure B.15

The Equation of a CircleThe Distance Formula provides a convenient way to define circles. A circle ofradius r with center at the point is shown in Figure B.16. The point is on this circle if and only if its distance from the center is r. This meansthat

�h, k��x, y��h, k�

The Midpoint Formula

The midpoint of the line segment joining the points and isgiven by the Midpoint Formula

Midpoint � x1 � x2

2,

y1 � y2

2 .

�x2, y2��x1, y1�

333353_APPB1.qxp 1/22/07 8:32 AM Page A29


a circle in the plane consists of all points that are a given positive distancer from a fixed point Using the Distance Formula, you can express thisrelationship by saying that the point lies on the circle if and only if

By squaring each side of this equation, you obtain the standard form of theequation of a circle.

Figure B.16

Center: (h, k)

Point oncircle: (x, y)

Radius: r

x

y

��x � h�2 � � y � k�2 � r.

�x, y��h, k�.

�x, y�

Standard Form of the Equation of a Circle

The standard form of the equation of a circle is

The point is the center of the circle, and the positive number is theradius of the circle. The standard form of the equation of a circle whosecenter is the origin, is x2 � y2 � r2.�h, k� � �0, 0�,

r�h, k�

�x � h�2 � �y � k�2 � r2.

Example 7 Writing the Equation of a Circle

The point lies on a circle whose center is at as shown in FigureB.17. Write the standard form of the equation of this circle.

SolutionThe radius r of the circle is the distance between and

Substitute for and

Simplify.

Radius

Using and the equation of the circle is

Equation of circle

Substitute for and

Standard form


�x � 1�2 � �y � 2�2 � 20.

r.h, k, �x � ��1��2 � �y � 2�2 � ��20 �2

�x � h�2 � �y � k�2 � r2

r � �20,�h, k� � ��1, 2�

� �20

� �16 � 4

k.x, y, h, r � ��3 � ��1��2 � �4 � 2�2

�3, 4�.��1, 2�

��1, 2�,�3, 4�

(3, 4)

64−2−6

4

−2

−4

8

x

y

(−1, 2)

Figure B.17

333353_APPB1.qxp 1/22/07 8:32 AM Page A30


Example 8 shows how to translate points in a coordinate plane. The followingtransformed points are related to the original points as follows.

Original Point Transformed Point

The figures provided with Example 8 were not really essential to thesolution. Nevertheless, it is strongly recommended that you develop the habit ofincluding sketches with your solutions, even if they are not required, because theyserve as useful problem-solving tools.

��x, �y��x, y�

�x, �y��x, y�

��x, y��x, y�

Much of computer graphics,including this computer-generatedgoldfish tessellation, consists oftransformations of points in acoordinate plane. One type oftransformation, a translation, isillustrated in Example 8. Othertypes of transformations includereflections, rotations, and stretches.

Paul Morrell

is a reflection of theoriginal point in the -axis.y��x, y�

is a reflection of theoriginal point in the -axis.x�x, �y�

is a reflection of theoriginal point through the origin.��x, �y�

Example 8 Translating Points in the Plane

The triangle in Figure B.18 has vertices at the points and Shift the triangle three units to the right and two units upward and find thevertices of the shifted triangle, as shown in Figure B.19.


SolutionTo shift the vertices three units to the right, add 3 to each of the x-coordinates. Toshift the vertices two units upward, add 2 to each of the y-coordinates.

Original Point Translated Point

Plotting the translated points and sketching the line segments between themproduces the shifted triangle shown in Figure B.19.


�2 � 3, 3 � 2� � �5, 5��2, 3�

�1 � 3, �4 � 2� � �4, �2��1, �4�

��1 � 3, 2 � 2� � �2, 4��1, 2�

−2 −1 1 2 3 5 6 7

4

3

2

1

5

−2−3−4

x

y

−2 −1 1 2 3 4 5 6 7

4

5

−2−3−4

(2, 3)

x

y

(1, −4)

(−1, 2)

�2, 3�.��1, 2�, �1, �4�,

333353_APPB1.qxp 1/22/07 8:32 AM Page A31


In Exercises 1 and 2, approximate the coordinates of thepoints.

1. 2.

In Exercises 3– 6, plot the points in the Cartesian plane.

3.

4.

5.6.

In Exercises 7–10, find the coordinates of the point.

7. The point is located five units to the left of the y-axis andfour units above the x-axis.

8. The point is located three units below the x-axis and twounits to the right of the y-axis.

9. The point is located six units below the x-axis and the coor-dinates of the point are equal.

10. The point is on the x-axis and 10 units to the left of the y-axis.

In Exercises 11–20, determine the quadrant(s) in whichis located so that the condition(s) is (are) satisfied.

11. and 12. and

13. and 14. and

15. 16.

17. and 18. and

19. 20.

In Exercises 21 and 22, sketch a scatter plot of the datashown in the table.

21. Sales The table shows the sales y (in millions of dollars)for Apple Computer, Inc. for the years 1997–2006.(Source: Value Line)

xy < 0xy > 0

y < 0�x > 0�y > 0x < 0

x > 4y < �5

y � 3x > 2y > 0x � �4

y < 0x < 0y < 0x > 0

�x, y�

�1, �12�, ��3

4, 2�, �3, �3�, �32, 43�

�3, 8�, �0.5, �1�, �5, �6�, ��2, �2.5��4, �2�, �0, 0�, ��4, 0�, ��5, �5��4, 2�, ��3, �6�, �0, 5�, �1, �4�

A

B

C

Dx

y

2−2−4−6

2

4

−2

−4

A

B C

D

2−2−4−6 4

2

−2

−4

4

6

x

y

B.1 Exercises See www.CalcChat.com for worked-out solutions to odd-numbered exercises.

Vocabulary Check

1. Match each term with its definition.

(a) x-axis (i) point of intersection of vertical axis and horizontal axis

(b) y-axis (ii) directed distance from the x-axis

(c) origin (iii) horizontal real number line

(d) quadrants (iv) four regions of the coordinate plane

(e) x-coordinate (v) directed distance from the y-axis

(f) y-coordinate (vi) vertical real number line

In Exercises 2–5, fill in the blanks.

2. An ordered pair of real numbers can be represented in a plane called the rectangular coordinate system or the _______ plane.

3. The _______ is a result derived from the Pythagorean Theorem.

4. Finding the average values of the respective coordinates of the two endpoints of a line segment in a coordinate plane is alsoknown as using the _______ .

5. The standard form of the equation of a circle is _______ , where the point is the _______ of the circle and the positivenumber r is the _______ of the circle.

�h, k�

YearSales, y

(in millions of dollars)

1997 7,081

1998 5,941

1999 6,134

2000 7,983

2001 5,363

2002 5,742

2003 6,207

2004 8,279

2005 13,900

2006 16,600

333353_APPB1.qxp 1/22/07 8:32 AM Page A32


22. Meteorology The table shows the lowest temperature onrecord (in degrees Fahrenheit) in Duluth, Minnesota foreach month where represents January. (Source:NOAA)

In Exercises 23–32, find the distance between the pointsalgebraically and verify graphically by using centimetergraph paper and a centimeter ruler.

23.

24.

25.

26.

27.

28.

29.

30.

31.

32.

In Exercises 33–36, (a) find the length of each side of the right triangle and (b) show that these lengths satisfythe Pythagorean Theorem.

33. 34.

35. 36.

In Exercises 37–44, show that the points form the vertices ofthe polygon.

37. Right triangle:

38. Right triangle:

39. Isosceles triangle:

40. Isosceles triangle:

41. Parallelogram:

42. Parallelogram:

43. Rectangle: (Hint: Show thatthe diagonals are of equal length.)

44. Rectangle: (Hint: Show that thediagonals are of equal length.)

In Exercises 45–54, (a) plot the points, (b) find the distancebetween the points, and (c) find the midpoint of the line seg-ment joining the points.

45. 46.

47.

48.

49.

50.

51.

52.

53.

54.

Revenue In Exercises 55 and 56, use the Midpoint Formulato estimate the annual revenues (in millions of dollars) forWendy’s Intl., Inc. and Papa John’s Intl. in 2003. The revenues for the two companies in 2000 and 2006 are shownin the tables. Assume that the revenues followed a linearpattern. (Source: Value Line)

55. Wendy’s Intl., Inc.

��16.8, 12.3�, �5.6, 4.9��6.2, 5.4�, ��3.7, 1.8��1

3, �13�, ��1

6, �12�

� 12, 1�, ��5

2, 43��2, 10�, �10, 2��1, 2�, �5, 4��7, �4�, �2, 8��4, 10�, �4, �5�

�1, 12�, �6, 0��1, 1�, �9, 7�

�2, 4�, �3, 1�, �1, 2�, �4, 3�

��5, 6�, �0, 8�, ��3, 1�, �2, 3��0, 1�, �3, 7�, �4, 4�, �1, �2��2, 5�, �0, 9�, ��2, 0�, �0, �4�

�2, 3�, �4, 9�, ��2, 7��1, �3�, �3, 2�, ��2, 4�

��1, 3�, �3, 5�, �5, 1��4, 0�, �2, 1�, ��1, �5�

(1, 5)

6

2

−2

4

x

y

(1, −2)

(5, −2)

(9, 4)

(9, 1)

(−1, 1) 6 8

2

4

6

x

y

4 8

8

4

(13, 5)

(1, 0)

(13, 0)x

y

54321

1

2

3

4

5 (4, 5)

(4, 2)(0, 2)

x

y

�9.5, �2.6�, ��3.9, 8.2��4.2, 3.1�, ��12.5, 4.8��2

3, 3�, ��1, 54��1

2, 43�, �2, �1��8, 5�, �0, 20��2, 6�, �3, �6��3, �4�, ��3, 6��3, �1�, �2, �1��1, 4�, �8, 4��6, �3�, �6, 5�

x � 1x,y

Month, x Temperature, y

1 �39

2 �39

3 �29

4 �5

5 17

6 27

7 35

8 32

9 22

10 8

11 �2312 �34

YearAnnual revenue


2000 2237

2006 3950

333353_APPB1.qxp 1/22/07 8:33 AM Page A33


56. Papa John’s Intl.

57. Exploration A line segment has as one endpointand as its midpoint. Find the other endpoint of the line segment in terms of and Use theresult to find the coordinates of the endpoint of a linesegment if the coordinates of the other endpoint andmidpoint are, respectively,

(a)

(b)

58. Exploration Use the Midpoint Formula three times tofind the three points that divide the line segment joining

and into four parts. Use the result to find thepoints that divide the line segment joining the given pointsinto four equal parts.

(a)

(b)

In Exercises 59–72, write the standard form of the equationof the specified circle.

59. Center: radius: 3



62. Center: radius:

63. Center: solution point:

64. Center: solution point:

65. Endpoints of a diameter:

66. Endpoints of a diameter:

67. Center: tangent to the x-axis

68. Center: tangent to the y-axis

69. The circle inscribed in the square with vertices and

70. The circle inscribed in the square with vertices and

71. 72.

In Exercises 73 –78, find the center and radius, and sketchthe circle.

73. 74.

75. 76.

77. 78.

In Exercises 79–82, the polygon is shifted to a new positionin the plane. Find the coordinates of the vertices of the polygon in the new position.

79. 80.

81. Original coordinates of vertices:

Shift: three units upward, one unit to the left

82. Original coordinates of vertices:

Shift: two units downward, three units to the left

Analyzing Data In Exercises 83 and 84, refer to the scatterplot, which shows the mathematics entrance test scores xand the final examination scores y in an algebra course fora sample of 10 students.

83. Find the entrance exam score of any student with a finalexam score in the 80s.

84. Does a higher entrance exam score necessarily imply ahigher final exam score? Explain.

Mathematics entrance test score

Fina

l exa

min

atio

n sc

ore

20 30 40 50 60 70 80

50

60

70

80

90

100

(22, 53)(40, 66)

(44, 79)

(53, 76)

(65, 83)

(48, 90) (58, 93)

(29, 74)

ReportCard

Math.....A

English..A

Science..B

PhysEd...A

(35, 57)

(76, 99)

x

y

�1, �1�, �3, 2�, �1, �2�

�0, 2�, �3, 5�, (5, 2�, �2, �1�

3 51−7

5

7

−3

x

3 un

its

6 units

y

(−3, 6) (−1, 3)

(−5, 3)(−3, 0)

4

2−2−4

2 units

5 un

its

y

(−1, −1)

(−2, −4)(2, −3)

x

�x �23�2

� � y �14�2

�259�x �

12�2 � �y �

12�2 �

94

x 2 � �y � 1�2 � 49�x � 1�2 � �y � 3�2 � 4

x 2 � y 2 � 16x 2 � y 2 � 25

x

y

−2−4−6−2

2

4

x

y

2 4

−6

4

��12, �10��8, �10�,�8, 10�,��12, 10�,

�7, �10��1, �10�,��1, �2�,�7, �2�,

�3, �2�;��2, 1�;

��4, �1�, �4, 1��0, 0�, �6, 8�

��1, 1��3, �2�;�0, 0��1, 2�;

13�0, 13�;

�2, �1�;�0, 0�;�0, 0�;

��2, �3�, �0, 0��1, �2�, �4, �1�

�x2, y2��x1, y1�

��5, 11�, �2, 4��1, �2�, �4, �1�

ym.x1, y1, xm,�x2, y2��xm, ym�

�x1, y1�

YearAnnual revenue


2000 945

2006 1005

333353_APPB1.qxp 1/22/07 8:33 AM Page A34


85. Rock and Roll Hall of Fame The graph shows thenumbers of recording artists inducted into the Rock andRoll Hall of Fame from 1986 to 2006.

(a) Describe any trends in the data. From these trends, pre-dict the number of artists that will be elected in 2007.

(b) Why do you think the numbers elected in 1986 and1987 were greater than in other years?

86. Flying Distance A jet plane flies from Naples, Italy in astraight line to Rome, Italy, which is 120 kilometers northand 150 kilometers west of Naples. How far does the planefly?

87. Sports In a football game, a quarterback throws a passfrom the 15-yard line, 10 yards from the sideline, as shownin the figure. The pass is caught on the 40-yard line,45 yards from the same sideline. How long is the pass?

88. Sports A major league baseball diamond is a square with90-foot sides. Place a coordinate system over the baseballdiamond so that home plate is at the origin and the firstbase line lies on the positive x-axis (see figure). Let oneunit in the coordinate plane represent one foot. The rightfielder fields the ball at the point . How far doesthe right fielder have to throw the ball to get a runner out athome plate? How far does the right fielder have to throwthe ball to get a runner out at third base? (Round youranswers to one decimal place.)

Figure for 88

89. Boating A yacht named Beach Lover leaves port at noonand travels due north at 16 miles per hour. At the same timeanother yacht, The Fisherman, leaves the same port andtravels west at 12 miles per hour.

(a) Using graph paper, plot the coordinates of each yacht at2 P.M. and 4 P.M. Let the port be at the origin of yourcoordinate system.

(b) Find the distance between the yachts at 2 P.M. and 4 P.M.Are the yachts twice as far from each other at 4 P.M. asthey were at 2 P.M.?

90. Make a Conjecture Plot the points andon a rectangular coordinate system. Then change

the signs of the indicated coordinate(s) of each point andplot the three new points on the same rectangular coordi-nate system. Make a conjecture about the location of apoint when each of the following occurs.

(a) The sign of the -coordinate is changed.

(b) The sign of the -coordinate is changed.

(c) The signs of both the and -coordinates are changed.

91. Show that the coordinates andform the vertices of an equilateral triangle.

92. Show that the coordinates and form the vertices of a right triangle.

Synthesis

True or False? In Exercises 93–95, determine whether thestatement is true or false. Justify your answer.

93. In order to divide a line segment into 16 equal parts, youwould have to use the Midpoint Formula 16 times.

94. The points and represent thevertices of an isosceles triangle.

95. If four points represent the vertices of a polygon, and thefour sides are equal, then the polygon must be a square.

96. Think About It What is the -coordinate of any point onthe -axis? What is the -coordinate of any point on the -axis?

97. Think About It When plotting points on the rectangularcoordinate system, is it true that the scales on the and

axes must be the same? Explain.y-x-

yxx

y

��5, 1��8, 4�, �2, 11�

�2, �4��4, 7�,��2, �1�,�2 � 2�3, 0�

�2 � 2�3, 0�,�2, 6�,

yx-

y

x

�7, �3��2, 1�, ��3, 5�,

10050 150 200 250 300

50

100

150

(0, 0)

(0, 90)

(300, 25)

x

y

Dis

tanc

e (i

n fe

et)

�300, 25�

Distance (in yards)

Dis

tanc

e (i

n ya

rds)

10 20 30 40 50

10

20

30

40

50

(10, 15)

(45, 40)

Year

Num

ber

indu

cted

2

6

10

14

1986 1989 1992 1995 1998 2001 2004

4

8

12

16

333353_APPB1.qxp 1/22/07 8:33 AM Page A35


B.2 Graphs of Equations

The Graph of an EquationNews magazines often show graphs comparing the rate of inflation, the federaldeficit, or the unemployment rate to the time of year. Businesses use graphs toreport monthly sales statistics. Such graphs provide geometric pictures of the wayone quantity changes with respect to another. Frequently, the relationship betweentwo quantities is expressed as an equation. This section introduces the basicprocedure for determining the geometric picture associated with an equation.

For an equation in the variables and a point is a solution point ifsubstitution of for and for satisfies the equation. Most equations haveinfinitely many solution points. For example, the equation hassolution points and so on. The set of all solutionpoints of an equation is the graph of the equation.

�0, 5�, �1, 2�, �2, �1�, �3, �4�,3x � y � 5

ybxa�a, b�y,x

Example 1 Determining Solution Points

Determine whether (a) and (b) lie on the graph of

Solution

a. Write original equation.

Substitute 2 for and 13 for

is a solution. ✓

The point does lie on the graph of because it is a solutionpoint of the equation.

b. Write original equation.

Substitute for and for

is not a solution.

The point does not lie on the graph of because it is nota solution point of the equation.

Now try Exercise 3.

The basic technique used for sketching the graph of an equation is the point-plotting method.

y � 10x � 7��1, �3�

��1, �3� �3 � �17

y.�3x�1 �3 �?

10��1� � 7

y � 10x � 7

y � 10x � 7�2, 13�

�2, 13� 13 � 13

y.x 13 �?

10�2� � 7

y � 10x � 7

y � 10x � 7.��1, �3��2, 13�

Sketching the Graph of an Equation by Point Plotting

1. If possible, rewrite the equation so that one of the variables is isolated on one side of the equation.

2. Make a table of values showing several solution points.

3. Plot these points on a rectangular coordinate system.

4. Connect the points with a smooth curve or line.

What you should learn� Sketch graphs of equations by point

plotting.

� Graph equations using a graphing utility.

� Use graphs of equations to solve real-life

problems.

Why you should learn itThe graph of an equation can help you see

relationships between real-life quantities. For

example, in Exercise 74 on page A46, a graph

can be used to estimate the life expectancies

of children born in the years 1948 and 2010.

333353_APPB2.qxd 1/22/07 8:34 AM Page A36

Appendix B.2 Graphs of Equations A37

Figure B.20

(a)

(b)

Figure B.21

Example 3 Sketching a Graph by Point Plotting

Use point plotting and graph paper to sketch the graph of

SolutionBecause the equation is already solved for y, make a table of values by choosingseveral convenient values of and calculating the corresponding values of

Next, plot the corresponding solution points, as shown in Figure B.21(a). Finally,connect the points with a smooth curve, as shown in Figure B.21(b). This graphis called a parabola. You will study parabolas in Section 2.1.

Now try Exercise 8.

In this text, you will study two basic ways to create graphs: by hand andusing a graphing utility. For instance, the graphs in Figures B.20 and B.21 were sketched by hand and the graph in Figure B.25 was created using a graphingutility.

y.x

y � x2 � 2.

x �1 0 1 2 3

y � 6 � 3x 9 6 3 0 �3

Solution point ��1, 9� �0, 6� �1, 3� �2, 0� �3, �3�

x �2 �1 0 1 2 3

y � x2 � 2 2 �1 �2 �1 2 7

Solution point ��2, 2� ��1, �1� �0, �2� �1, �1� �2, 2� �3, 7�

Example 2 Sketching a Graph by Point Plotting

Use point plotting and graph paper to sketch the graph of

SolutionIn this case you can isolate the variable y.

Solve equation for y.

Using negative, zero, and positive values for you can obtain the following tableof values (solution points).

Next, plot these points and connect them, as shown in Figure B.20. It appears thatthe graph is a straight line. You will study lines extensively in Section 1.1.

Now try Exercise 7.

The points at which a graph touches or crosses an axis are called the inter-cepts of the graph. For instance, in Example 2 the point is the -interceptof the graph because the graph crosses the -axis at that point. The point isthe -intercept of the graph because the graph crosses the -axis at that point.xx

�2, 0�yy�0, 6�

x,

y � 6 � 3x

3x � y � 6.

333353_APPB2.qxd 1/22/07 8:34 AM Page A37


Using a Graphing UtilityOne of the disadvantages of the point-plotting method is that to get a good ideaabout the shape of a graph, you need to plot many points. With only a few points,you could misrepresent the graph of an equation. For instance, consider theequation

Suppose you plotted only five points: andas shown in Figure B.22(a). From these five points, you might assume that

the graph of the equation is a line. That, however, is not correct. By plotting several more points and connecting the points with a smooth curve, you can seethat the actual graph is not a line at all, as shown in Figure B.22(b).

(a) (b)

Figure B.22

From this, you can see that the point-plotting method leaves you with adilemma. This method can be very inaccurate if only a few points are plotted, andit is very time-consuming to plot a dozen (or more) points. Technology can helpsolve this dilemma. Plotting several (even several hundred) points on a rectangu-lar coordinate system is something that a computer or calculator can do easily.

�3, 3�,�1, 1�,�0, 0�,��1, �1�,��3, �3�,

y �1

30 x�x4 � 10x2 � 39�.

Using a Graphing Utility to Graph an Equation

To graph an equation involving and on a graphing utility, use the following procedure.

1. Rewrite the equation so that is isolated on the left side.

2. Enter the equation in the graphing utility.

3. Determine a viewing window that shows all important features of the graph.

4. Graph the equation.

y

yx

This section presents a briefoverview of how to use a graphing utility to graph anequation. For more extensivecoverage of this topic, seeAppendix A and the GraphingTechnology Guide at this textbook’s Online Study Center.

TECHNOLOGY SUPPORT

The point-plotting method is the method used by allgraphing utilities. Each computer or calculator screen is made up of a grid ofhundreds or thousands of small areas called pixels. Screens that have manypixels per square inch are said to have a higher resolution than screens withfewer pixels.

TECHNOLOGY TIP

333353_APPB2.qxd 1/22/07 8:34 AM Page A38

Example 4 Using a Graphing Utility to Graph an Equation

Use a graphing utility to graph

SolutionTo begin, solve the equation for y in terms of x.

Write original equation.

Subtract from each side.

Divide each side by 2.

Enter this equation in a graphing utility (see Figure B.23). Using a standard viewingwindow (see Figure B.24), you can obtain the graph shown in Figure B.25.


Figure B.25


10

−10

−10 10

2y + x3 = 4x

y � �x3

2� 2x

x3 2y � �x3 � 4x

2y � x3 � 4x

2y � x3 � 4x.

00 0.5

0.5

−3

0 6

3

−1.5

−1.2 1.2

1.5

(a) (b) (c)

Figure B.26

T E C H N O L O G Y T I P

By choosing different viewing windows for a graph,it is possible to obtain very different impressions of the graph’s shape. Forinstance, Figure B.26 shows three different viewing windows for the graph ofthe equation in Example 4. However, none of these views shows all of theimportant features of the graph as does Figure B.25. For instructions on howto set up a viewing window, see Appendix A; for specific keystrokes, go tothis textbook’s Online Study Center.

TECHNOLOGY TIP

Many graphing utilities are capa-ble of creating a table of valuessuch as the following, whichshows some points of the graph in Figure B.25. For instructions on how to use the table feature,see Appendix A; for specific keystrokes, go to this textbook’sOnline Study Center.


333353_APPB2.qxd 1/22/07 8:34 AM Page A39


Example 5 Using a Graphing Utility to Graph a Circle


SolutionThe graph of is a circle whose center is the origin and whose radiusis 3. To graph the equation, begin by solving the equation for y.



Take the square root of each side.

Remember that when you take the square root of a variable expression, you mustaccount for both the positive and negative solutions. The graph of

Upper semicircle

is the upper semicircle. The graph of

Lower semicircle

is the lower semicircle. Enter both equations in your graphing utility and generatethe resulting graphs. In Figure B.27, note that if you use a standard viewingwindow, the two graphs do not appear to form a circle. You can overcome thisproblem by using a square setting, in which the horizontal and vertical tick markshave equal spacing, as shown in Figure B.28. On many graphing utilities, a squaresetting can be obtained by using a to ratio of 2 to 3. For instance, in FigureB.28, the to ratio is



−4

−6 6

4

−10

−10 10

10

Ymax � Ymin

Xmax � Xmin�

4 � ��4�6 � ��6�

�8

12�

2

3.

xyxy

y � ��9 � x2

y � �9 � x2

y � ±�9 � x2

x2 y2 � 9 � x2

x2 � y2 � 9

x2 � y2 � 9

x2 � y2 � 9.

The standard viewing window on many graphingutilities does not give a true geometric perspective because the screen isrectangular, which distorts the image. That is, perpendicular lines will notappear to be perpendicular and circles will not appear to be circular. To overcome this, you can use a square setting, as demonstrated in Example 5.

TECHNOLOGY TIP

Notice that when you graph acircle by graphing two separateequations for y, your graphingutility may not connect the twosemicircles. This is because somegraphing utilities are limited intheir resolution. So, in this text,a blue curve is placed behind thegraphing utility’s display toindicate where the graph shouldappear.


Prerequisite Skills

To review the equation of a circle, see

Section B.1.

333353_APPB2.qxd 1/22/07 8:34 AM Page A40

ApplicationsThroughout this course, you will learn that there are many ways to approach aproblem. Two of the three common approaches are illustrated in Example 6.

An Algebraic Approach: Use the rules of algebra.

A Graphical Approach: Draw and use a graph.

A Numerical Approach: Construct and use a table.

You should develop the habit of using at least two approaches to solve every prob-lem in order to build your intuition and to check that your answer is reasonable.

The following two applications show how to develop mathematical modelsto represent real-world situations. You will see that both a graphing utility andalgebra can be used to understand and solve the problems posed.

Example 6 Running a Marathon

A runner runs at a constant rate of 4.9 miles per hour. The verbal model and algebraic equation relating distance run and elapsed time are as follows.

Equation:

a. Determine how far the runner can run in 3.1 hours.

b. Determine how long it will take to run a 26.2-mile marathon.

d � 4.9tTime�Rate�DistanceVerbalModel:

Graphical Solutiona. Use a graphing utility to graph the equation

(Represent by and by ) Be sure to use a viewingwindow that shows the graph at Then use thevalue feature or the zoom and trace features of thegraphing utility to estimate that when the distance is miles, as shown in Figure B.29(a).

b. Adjust the viewing window so that it shows the graph atUse the zoom and trace features to estimate

that when the time is hours, as shownin Figure B.29(b).

(a) (b)

Figure B.29

Note that the viewing window on your graphing utilitymay differ slightly from those shown in Figure B.29.

245 6

28

112 4

19

x � 5.3y � 26.2,y � 26.2.

y � 15.2x � 3.1,

x � 3.1.x.tyd

d � 4.9t.

Algebraic Solutiona. To begin, find how far the runner can run in 3.1 hours

by substituting 3.1 for in the equation.


Substitute 3.1 for t.

Use a calculator.

So, the runner can run about 15.2 miles in 3.1 hours.Use estimation to check your answer. Because 4.9 isabout 5 and 3.1 is about 3, the distance is about

So, 15.2 is reasonable.b. You can find how long it will take to run a 26.2-mile

marathon as follows. (For help with solving linearequations, see Appendix E.)


Substitute 26.2 for d.

Divide each side by 4.9.

Use a calculator.

So, it will take about 5.3 hours to run 26.2 miles.


5.3 � t

26.24.9

� t

26.2 � 4.9t

d � 4.9t

5�3� � 15.

� 15.2

� 4.9�3.1�

d � 4.9t

t

TECHNOLOGY SUPPORT

For instructions on how to use the value feature, the zoom andtrace features, and the tablefeature of a graphing utility,see Appendix A; for specific keystrokes, go to this textbook’sOnline Study Center.


333353_APPB2.qxd 1/22/07 8:34 AM Page A41


Graphical Solutiona. You can use a graphing utility to graph

and then estimate the wageswhen . Be sure to use a viewing windowthat shows the graph for and Then,by using the value feature or the zoom and tracefeatures near you can estimate that thewages are about $2148, as shown in Figure B.34(a).

b. Use the graphing utility to find the value along the -axis (sales) that corresponds to a -value of 2225

(wages). Using the zoom and trace features, youcan estimate the sales to be about $2250, as shownin Figure B.34(b).

(a) Zoom near

(b) Zoom near

Figure B.34y � 2225

15001000 3350

3050

x � 1480

21001400 1500

2200

yx

x � 1480,

y > 2000.x ≥ 0x � 1480

y � 2000 � 0.1x

Numerical Solutiona. To find the wages in August, evaluate the equation when


Substitute 1480 for x.

Simplify.

So, your wages in August are $2148.

b. You can use the table feature of a graphing utility to createa table that shows the wages for different sales amounts.First enter the equation in the graphing utility. Then set upa table, as shown in Figure B.30. The graphing utility pro-duces the table shown in Figure B.31.


From the table, you can see that wages of $2225 result fromsales between $2200 and $2300. You can improve this esti-mate by setting up the table shown in Figure B.32. Thegraphing utility produces the table shown in Figure B.33.


From the table, you can see that wages of $2225 result fromsales of $2250.


� 2148

� 2000 � 0.1�1480�

y � 2000 � 0.1x

x � 1480.

Example 7 Monthly Wage

You receive a monthly salary of $2000 plus a commission of 10% of sales. Theverbal model and algebraic equation relating the wages, the salary, and thecommission are as follows.

Equation:

a. Sales are $1480 in August. What are your wages for that month?

b. You receive $2225 for September. What are your sales for that month?

y � 2000 � 0.1x

Commission on sales�Salary�WagesVerbalModel:

333353_APPB2.qxd 1/22/07 2:35 PM Page A42


In Exercises 1–6, determine whether each point lies on thegraph of the equation.

Equation Points

1. (a) (b)

2. (a) (b)

3. (a) (b)

4. (a) (b)

5. (a) (b)

6. (a) (b)

In Exercises 7 and 8, complete the table. Use the resultingsolution points to sketch the graph of the equation. Use agraphing utility to verify the graph.

7.

8.

9. Exploration

(a) Complete the table for the equation

(b) Use the solution points to sketch the graph. Then use agraphing utility to verify the graph.

(c) Repeat parts (a) and (b) for the equation Describe any differences between the graphs.

10. Exploration

(a) Complete the table for the equation

(b) Use the solution points to sketch the graph. Then use agraphing utility to verify the graph.

(c) Continue the table in part (a) for -values of 5, 10, 20,and 40. What is the value of approaching? Can benegative for positive values of Explain.

In Exercises 11–16, match the equation with its graph. [Thegraphs are labeled (a), (b), (c), (d), (e), and (f).]

(a) (b)

(c) (d)

(e) (f)

11. 12.

13. 14.

15. 16. y � �x� � 3y � 2�x

y � �9 � x 2y � x 2 � 2x

y � 4 � x2y � 2x � 3

−6

−3

6

5

−6

−3

6

5

−6

−4

6

4

−2 10

−1

7

6

−2

−6 6

−6

−5

6

3

x?yy

x

y �6x

x2 � 1.

y � �14 x � 3.

y �14 x � 3.

2x � y � x2

3x � 2y � 2

��3, 9��2, �163 �y �

13 x3 � 2x2

��4, 2��3, �2�x 2 � y 2 � 20

�1, �1��1, 2�2x � y � 3 � 0

�1.2, 3.2��1, 5�y � 4 � �x � 2��2, 8��2, 0�y � x 2 � 3x � 2

�5, 3��0, 2�y � �x � 4


x �2 �1 0 1 2

y

x �2 0 23 1 2

y

Solution point

x �1 0 1 2 3

y

Solution point

x �2 �1 0 1 2

y

Vocabulary Check

Fill in the blanks.

1. For an equation in x and y, if substitution of for and for satisfies the equation, then the point is a _______ .

2. The set of all solution points of an equation is the _______ of the equation.

3. The points at which a graph touches or crosses an axis are called the _______ of the graph.

�a, b�ybxa

333353_APPB2.qxd 1/22/07 8:34 AM Page A43


In Exercises 17–30, sketch the graph of the equation.

17. 18.

19. 20.

21. 22.

23. 24.

25. 26.

27. 28.

29. 30.

In Exercises 31–44, use a graphing utility to graph theequation. Use a standard viewing window. Approximate anyx- or y-intercepts of the graph.

31. 32.

33. 34.

35. 36.

37.

38.

39.

40.

41.

42.

43.

44.

In Exercises 45–48, use a graphing utility to graph theequation. Begin by using a standard viewing window. Thengraph the equation a second time using the specified viewing window. Which viewing window is better? Explain.

45. 46.

47. 48.

In Exercises 49–54, describe the viewing window of thegraph shown.

49. 50.

51. 52.

53. 54.

In Exercises 55–58, explain how to use a graphing utility to verify that Identify the rule of algebra that is illustrated.

55.

56.

57.

58.

In Exercises 59–62, use a graphing utility to graph theequation. Use the trace feature of the graphing utility toapproximate the unknown coordinate of each solution pointaccurate to two decimal places. (Hint: You may need to usethe zoom feature of the graphing utility to obtain therequired accuracy.)

59. 60.

(a) (a)

(b) (b)

61. 62.

(a) (a)

(b) (b) �x, 1.5��x, �4��2, y��0.5, y�

y � �x 2 � 6x � 5�y � x 5 � 5x

�x, 20��x, 3��2.25, y��2, y�

y � x 3�x � 3�y � �5 � x

y2 � 1

y1 � �x � 3� �1

x � 3

y2 � 2�x 2 � 1�

y1 �1

5�10�x 2 � 1��

y2 �32x � 1

y1 �12x � �x � 1�

y2 �14x 2 � 2

y1 �14�x 2 � 8�

y1 � y2.

y � 8 3�x � 6y � �x� � �x � 10�

y � x 3 � 3x 2 � 4y � �x � 2 � 1

y � 4x 2 � 25y � �10x � 50

Xmin = -6Xmax = 6Xscl = 1Ymin = -5Ymax = 50Yscl = 5


y � 4�x � 5��4 � xy � �x2 � 10x � 5


Xmin = 0Xmax = 6Xscl = 1Ymin = 0Ymax = 10Yscl = 1

y � �3x � 50y �52x � 5

x3 � y � 1

y � 4x � x2�x � 4�2y � x2 � 8 � 2x

x2 � y � 4x � 3

y � 3�x � 1

y � 3�x � 8

y � �6 � x��x

y � x�x � 3

y �4

xy �

2x

x � 1

y �23 x � 1y � 3 �

12 x

y � x � 1y � x � 7

x � y 2 � 4x � y 2 � 1

y � 5 � �x�y � �x � 2�y � �1 � xy � �x � 3

y � x 3 � 3y � x 3 � 2

y � �x 2 � 4xy � x 2 � 3x

y � x 2 � 1y � 2 � x 2

y � 2x � 3y � �4x � 1

333353_APPB2.qxd 1/22/07 8:34 AM Page A44

In Exercises 63–66, solve for y and use a graphing utility tograph each of the resulting equations in the same viewingwindow. (Adjust the viewing window so that the circleappears circular.)

63.

64.

65.

66.

In Exercises 67 and 68, determine which equation is the bestchoice for the graph of the circle shown.

67.

(a)

(b)

(c)

(d)

68.

(a)

(b)

(c)

(d)

In Exercises 69 and 70, determine whether each point lies on the graph of the circle. (There may be more than one correct answer.)

69.

(a) (b)

(c) (d)

70.

(a) (b)

(c) (d)

71. Depreciation A manufacturing plant purchases a newmolding machine for $225,000. The depreciated value(decreased value) after years is for

(a) Use the constraints of the model to graph the equationusing an appropriate viewing window.

(b) Use the value feature or the zoom and trace features ofa graphing utility to determine the value of when

Verify your answer algebraically.

(c) Use the value feature or the zoom and trace features ofa graphing utility to determine the value of when


72. Consumerism You buy a personal watercraft for $8100.The depreciated value after years is for

(a) Use the constraints of the model to graph the equationusing an appropriate viewing window.

(b) Use the zoom and trace features of a graphing utility todetermine the value of when Verifyyour answer algebraically.

(c) Use the value feature or the zoom and trace features ofa graphing utility to determine the value of when


73. Data Analysis The table shows the median (middle) salesprices (in thousands of dollars) of new one-family homes inthe southern United States from 1995 to 2004. (Sources:U.S. Census Bureau and U.S. Department of Housing andUrban Development)

A model for the median sales price during this period isgiven by

where represents the sales price and represents the year,with corresponding to 1995.t � 5

ty

y � �0.0049t3 � 0.443t2 � 0.75t � 116.7, 5 ≤ t ≤ 14

t � 5.5.y

y � 5545.25.t

0 ≤ t ≤ 6.y � 8100 � 929t,ty

t � 2.35.y

t � 5.8.y

0 ≤ t ≤ 8.y � 225,000 � 20,000t,ty

��1, 3 � 2�6 ��1, �1��0, 0��2, 3�

�x � 2�2 � �y � 3�2 � 25

�0, 2 � 2�6 ��5, �1��2, 6��1, 2�

�x � 1�2 � �y � 2�2 � 25

�x � 2�2 � �y � 3�2 � 4

�x � 2�2 � �y � 3�2 � 16

�x � 2�2 � �y � 3�2 � 16

�x � 2�2 � �y � 3�2 � 4

y

x

�x � 1�2 � �y � 2�2 � 4

�x � 1�2 � �y � 2�2 � 16

�x � 1�2 � �y � 2�2 � 4

�x � 1�2 � �y � 2�2 � 4

y

x

�x � 3�2 � �y � 1�2 � 25

�x � 1�2 � �y � 2�2 � 4

x2 � y 2 � 36

x 2 � y 2 � 16

Year Median sales price, y

1995 124.5

1996 126.2

1997 129.6

1998 135.8

1999 145.9

2000 148.0

2001 155.4

2002 163.4

2003 168.1

2004 181.1


333353_APPB2.qxd 1/22/07 8:34 AM Page A45


(a) Use the model and the table feature of a graphing utility to find the median sales prices from 1995 to2004. How well does the model fit the data? Explain.

(b) Use a graphing utility to graph the data from the tableand the model in the same viewing window. How welldoes the model fit the data? Explain.

(c) Use the model to estimate the median sales prices in2008 and 2010. Do the values seem reasonable?Explain.

(d) Use the zoom and trace features of a graphing utility todetermine during which year(s) the median sales pricewas approximately $150,000.

74. Population Statistics The table shows the lifeexpectancies of a child (at birth) in the United States forselected years from 1930 to 2000. (Source: U.S. NationalCenter for Health Statistics)

A model for the life expectancy during this period is givenby

where represents the life expectancy and is the time inyears, with corresponding to 1930.

(a) Use a graphing utility to graph the data from the tableabove and the model in the same viewing window. Howwell does the model fit the data? Explain.

(b) What does the -intercept of the graph of the modelrepresent?

(c) Use the zoom and trace features of a graphing utility todetermine the year when the life expectancy was 73.2.Verify your answer algebraically.

(d) Determine the life expectancy in 1948 both graphical-ly and algebraically.

(e) Use the model to estimate the life expectancy of a childborn in 2010.

75. Geometry A rectangle of length and width has aperimeter of 12 meters.

(a) Draw a diagram that represents the rectangle. Use thespecified variables to label its sides.

(b) Show that the width of the rectangle is andthat its area is

(c) Use a graphing utility to graph the area equation.

(d) Use the zoom and trace features of a graphing utility todetermine the value of when meters. Verifyyour answer algebraically.

(e) From the graph in part (c), estimate the dimensions ofthe rectangle that yield a maximum area.

76. Find the standard form of the equation of the circle forwhich the endpoints of a diameter are and

Synthesis

True or False? In Exercises 77 and 78, determine whetherthe statement is true or false. Justify your answer.

77. A parabola can have only one -intercept.

78. The graph of a linear equation can have either no -intercepts or only one -intercept.

79. Writing Explain how to find an appropriate viewingwindow for the graph of an equation.

80. Writing Your employer offers you a choice of wagescales: a monthly salary of $3000 plus commission of 7%of sales or a salary of $3400 plus a 5% commission. Writea short paragraph discussing how you would choose youroption. At what sales level would the options yield thesame salary?

81. Writing Given the equation write apossible explanation of what the equation could representin real life.

82. Writing Given the equation write apossible explanation of what the equation could representin real life.

y � �0.1x � 10,

y � 250x � 1000,

xx

x

�4, �6�.�0, 0�

w � 4.9A

A � x�6 � x�.w � 6 � x

wx

y

t � 0ty

0 ≤ t ≤ 70y �59.617 � 1.18t

1 � 0.012t,

Year Life expectancy, y

1930 59.7

1940 62.9

1950 68.2

1960 69.7

1970 70.8

1980 73.7

1990 75.4

2000 77.0

333353_APPB2.qxd 1/22/07 8:34 AM Page A46

B.3 Solving Equations Algebraically and Graphically

What you should learn� Solve linear equations.

� Find x- and y-intercepts of graphs of

equations.

� Find solutions of equations graphically.

� Find the points of intersection of two

graphs.

� Solve polynomial equations.

� Solve equations involving radicals,

fractions, or absolute values.

Why you should learn itKnowing how to solve equations algebraically

and graphically can help you solve real-life

problems. For instance, in Exercise 195 on

page A62, you will find the point of intersec-

tion of the graphs of two population models

both algebraically and graphically.

Appendix B.3 Solving Equations Algebraically and Graphically A47

Equations and Solutions of EquationsAn equation in x is a statement that two algebraic expressions are equal. Forexample, and are equations. To solve anequation in x means to find all values of x for which the equation is true. Suchvalues are solutions. For instance, is a solution of the equation

because is a true statement.The solutions of an equation depend on the kinds of numbers being consid-

ered. For instance, in the set of rational numbers, has no solutionbecause there is no rational number whose square is 10. However, in the set ofreal numbers, the equation has the two solutions and

An equation that is true for every real number in the domain (the domain isthe set of all real numbers for which the equation is defined) of the variableis called an identity. For example, is an identitybecause it is a true statement for any real value of x, and where

is an identity because it is true for any nonzero real value of x.An equation that is true for just some (or even none) of the real numbers in

the domain of the variable is called a conditional equation. The equationis conditional because and are the only values in the

domain that satisfy the equation. The equation is alsoconditional because there are no real values of x for which the equation is true.

A linear equation in one variable x is an equation that can be written in thestandard form where and are real numbers, with For areview of solving one- and two-step linear equations, see Appendix E.

To solve an equation involving fractional expressions, find the least commondenominator (LCD) of all terms in the equation and multiply every term by thisLCD. This procedure clears the equation of fractions, as demonstrated inExample 1.

a � 0.baax � b � 0,

2x � 1 � 2x � 3x � �3x � 3x2 � 9 � 0

x � 0,x��3x2� � 1��3x�,

x2 � 9 � �x � 3��x � 3�

��10.�10

x2 � 10

3�4� � 5 � 73x � 5 � 7x � 4

�2x � 4x2 � x � 6 � 0,3x � 5 � 7,

STUDY TIP

After solving an equation,you should check each solutionin the original equation. Forinstance, you can check thesolution to Example 1 asfollows.

✓ 2 � 2

813

�1813

�?

2

2413

3�

3�2413�4

�?

2

x3

�3x4

� 2

Example 1 Solving an Equation Involving Fractions

Solve

Solution


Multiply each term by the LCD of 12.

Divide out and multiply.

Combine like terms.



x �24

13

13x � 24

4x � 9x � 24

�12� x

3� �12�

3x

4� �12�2

x

3�

3x

4� 2

x

3�

3x

4� 2.

333353_APPB3.qxp 1/22/07 8:51 AM Page A47


Example 2 An Equation with an Extraneous Solution

Solve 1

x � 2�

3

x � 2�

6x

x2 � 4.

When multiplying or dividing an equation by a variable expression, it ispossible to introduce an extraneous solution—one that does not satisfy theoriginal equation. The next example demonstrates the importance of checkingyour solution when you have multiplied or divided by a variable expression.

Algebraic SolutionThe LCD is

Multiplying each term by the LCD and simplifying producesthe following.

Extraneous solution

A check of in the original equation shows that ityields a denominator of zero. So, is an extraneoussolution, and the original equation has no solution.


x � �2x � �2

x � �2

4x � �8

x � 2 � 3x � 6 � 6x

x � ±2 x � 2 � 3�x � 2� � 6x,

�3

x � 2 �x � 2��x � 2� �

6x

x2 � 4�x � 2��x � 2�

1

x � 2 �x � 2��x � 2�

x2 � 4 � �x � 2��x � 2�.

Graphical SolutionUse a graphing utility (in dot mode) to graph the leftand right sides of the equation,

and

in the same viewing window, as shown in Figure B.35.The graphs of the equations do not appear to intersect.This means that there is no point for which the left side of the equation is equal to the right side of the equation So, the equation appears to have no solution.

Figure B.35

−5

−6 9

5

x − 21

y1 =

x + 23 6x

y2 = −x2 − 4

y2.y1

y2 �3

x � 2�

6xx2 � 4

y1 �1

x � 2

Definition of Intercepts

1. The point is called an x-intercept of the graph of an equation ifit is a solution point of the equation. To find the -intercept(s), set equal to 0 and solve the equation for

2. The point is called a y-intercept of the graph of an equation ifit is a solution point of the equation. To find the -intercept(s), set equal to 0 and solve the equation for y.

xy�0, b�

x.yx

�a, 0�

Intercepts and SolutionsIn Section B.2, you learned that the intercepts of a graph are the points at whichthe graph intersects the or axis.y-x-

STUDY TIP

Recall that the least commondenominator of several rationalexpressions consists of the prod-uct of all prime factors in thedenominators, with each factorgiven the highest power of itsoccurrence in any denominator.

333353_APPB3.qxp 1/22/07 8:51 AM Page A48

Sometimes it is convenient to denote the intercept as simply the coordi-nate of the point rather than the point itself. Unless it is necessary to makea distinction, “intercept” will be used to mean either the point or the coordinate.

It is possible for a graph to have no intercepts, one intercept, or severalintercepts. For instance, consider the three graphs shown in Figure B.36.

Three x-Intercepts No x-InterceptsOne y-Intercept One y-Intercept No InterceptsFigure B.36

x

y

x

y

x

y

�a, 0�x-x-


Example 3 Finding x- and y-Intercepts

Find the - and -intercepts of the graph of

SolutionTo find the -intercept, let and solve for This produces

which implies that the graph has one -intercept: To find the -intercept,let and solve for This produces

which implies that the graph has one -intercept: See Figure B.37.

Figure B.37


The concepts of -intercepts and solutions of equations are closely related. Infact, the following statements are equivalent.

1. The point is an -intercept of the graph of an equation.

2. The number is a solution of the equation y � 0.a

x�a, 0�

x

−1

−1 5

3

0, 53 ((

(( , 0 52

2x + 3y = 5

�0, 53�.y

y �533y � 5

y.x � 0y�5

2, 0�.x

x �522x � 5

x.y � 0x

2x � 3y � 5.yx

333353_APPB3.qxp 1/22/07 8:51 AM Page A49


The close connection between -intercepts and solutions is crucial to yourstudy of algebra.You can take advantage of this connection in two ways. Use your algebraic equation-solving skills to find the -intercepts of a graph, and use your graphing skills to approximate the solutions of an equation.

Finding Solutions GraphicallyPolynomial equations of degree 1 or 2 can be solved in relatively straightforwardways. Solving polynomial equations of higher degree can, however, be quitedifficult, especially if you rely only on algebraic techniques. For such equations,a graphing utility can be very helpful.

Chapter 2 shows techniques for determining the number of solutions of apolynomial equation. For now, you should know that a polynomial equation ofdegree cannot have more than different solutions.nn

x

x

Graphical Approximations of Solutions of an Equation

1. Write the equation in general form, with the nonzero terms on one side of the equation and zero on the other side.

2. Use a graphing utility to graph the equation. Be sure the viewingwindow shows all the relevant features of the graph.

3. Use the zero or root feature or the zoom and trace features of thegraphing utility to approximate the intercepts of the graph.x-

y � 0,

For instructions on how to use the zero or root feature, seeAppendix A; for specifickeystrokes, go to this textbook’sOnline Study Center.

TECHNOLOGY SUPPORT

Example 4 Finding Solutions of an Equation Graphically

Use a graphing utility to approximate the solutions of

SolutionGraph the function You can see from the graph that there isone -intercept. It lies between and and is approximately By usingthe zero or root feature of a graphing utility, you can improve the approximation.Choose a left bound of (see Figure B.38) and a right bound of (see Figure B.39). To two-decimal-place accuracy, the solution is asshown in Figure B.40. Check this approximation on your calculator. You will findthat the value of is

Figure B.38 Figure B.39 Figure B.40


−4

−6 6

4

−4

−6 6

4

y � 2��1.48�3 � 3��1.48� � 2 � �0.04.y

x � �1.48,x � �1x � �2

�1.5.�1�2xy � 2x3 � 3x � 2.

2x3 � 3x � 2 � 0.

−4

−6 6

4

y = 2x3 − 3x + 2

333353_APPB3.qxp 1/22/07 8:51 AM Page A50


−0.01

4.29 4.32

0.01

Example 5 Approximating Solutions of an Equation Graphically

Use a graphing utility to approximate the solutions of

SolutionIn general form, this equation is

Equation in general form

So, you can begin by graphing

Function to be graphed

as shown in Figure B.41. This graph has two -intercepts, and by using the zoomand trace features you can approximate the corresponding solutions to be

and as shown in Figures B.42 and B.43.



−0.01

0.68 0.71

0.01

−6

−7 11

6y = x2 − 5x + 3

x � 4.30,x � 0.70

x

y � x2 � 5x � 3

x2 � 5x � 3 � 0.

x2 � 3 � 5x.

Remember that the more decimalplaces in the solution, the moreaccurate the solution is. You canreach the desired accuracy whenzooming in as follows.

• To approximate the zero to the nearest hundredth, set the

scale to 0.01.

• To approximate the zero to the nearest thousandth, set the scale to 0.001.x-

x-


Remember from Example 4 that the built-in zero orroot features of a graphing utility will approximate solutions of equations or

intercepts of graphs. If your graphing utility has such features, try using themto approximate the solutions in Example 5.x-

TECHNOLOGY TIP

You can also use a graphing calculator’s zoom andtrace features to approximate the solution(s) of an equation. Here are some suggestions for using the zoom-in feature of a graphing utility.

1. With each successive zoom-in, adjust the scale (if necessary) so that theresulting viewing window shows at least the two scale marks betweenwhich the solution lies.

2. The accuracy of the approximation will always be such that the error is lessthan the distance between two scale marks.

3. If you have a trace feature on your graphing utility, you can generally addone more decimal place of accuracy without changing the viewing window.

Unless stated otherwise, this book will approximate all real solutions with anerror of at most 0.01.

x-

TECHNOLOGY TIP

333353_APPB3.qxp 1/22/07 8:51 AM Page A51


Points of Intersection of Two GraphsAn ordered pair that is a solution of two different equations is called a pointof intersection of the graphs of the two equations. For instance, in Figure B.44you can see that the graphs of the following equations have two points ofintersection.

Equation 1

Equation 2

The point is a solution of both equations, and the point is a solu-tion of both equations. To check this algebraically, substitute and into each equation.

Check that is a solution.

Equation 1: Solution checks. ✓


Check that is a solution.



To find the points of intersection of the graphs of two equations, solve eachequation for (or ) and set the two results equal to each other. The resultingequation will be an equation in one variable that can be solved using standardprocedures, as shown in Example 6.

xy

y � �4�2 � 2�4� � 2 � 6

y � 4 � 2 � 6

�4, 6�

� 1 y � ��1�2 � 2��1� � 2

y � �1 � 2 � 1

��1, 1�

x � 4x � �1�4, 6��1, 1�

y � x2 � 2x � 2

y � x � 2

y

x−4 2 4 6 8

−2

−4

2

4

6

8

y = x2 − 2x − 2

y = x + 2

(4, 6)

(−1, 1)

Figure B.44

Example 6 Finding Points of Intersection

Find the points of intersection of the graphs of and 4x � y � 6.2x � 3y � �2

Algebraic SolutionTo begin, solve each equation for y to obtain

and

Next, set the two expressions for y equal to each other andsolve the resulting equation for as follows.

Equate expressions for

Multiply each side by 3.

Subtract and 2 from each side.

Divide each side by

When the value of each of the original equations is 2. So, the point of intersection is


�2, 2�.y-x � 2,

�10. x � 2

12x �10x � �20

2x � 2 � 12x � 18

y. 2

3 x �

2

3� 4x � 6

x,

y � 4x � 6.y �2

3x �

2

3

Graphical SolutionTo begin, solve each equation for y to obtain and Then use a graphing utility to graphboth equations in the same viewing window. In FigureB.45, the graphs appear to have one point of intersec-tion. Use the intersect feature of the graphing utility toapproximate the point of intersection to be

Figure B.45

−3

−6 6

5

y1 = x + 23

23

y2 = 4x − 6

�2, 2�.

y2 � 4x � 6.y1 �

23x �

23

For instructions on how to use theintersect feature, see Appendix A;for specific keystrokes, go to thistextbook’s Online Study Center.

TECHNOLOGY SUPPORT

333353_APPB3.qxp 1/22/07 8:51 AM Page A52


Example 7 Approximating Points of Intersection Graphically

Approximate the point(s) of intersection of the graphs of the following equations.

Equation 1 (quadratic function)

Equation 2 (cubic function)

SolutionBegin by using a graphing utility to graph both equations, as shown in FigureB.46. From this display, you can see that the two graphs have only one point ofintersection. Then, using the zoom and trace features, approximate the point ofintersection to be as shown in Figure B.47.

To test the reasonableness of this approximation, you can evaluate bothequations at

Quadratic Equation:

Cubic Equation:

Because both equations yield approximately the same -value, you can approxi-mate the coordinates of the point of intersection to be and


y � 7.25.x � �2.17y

y � ��2.17�3 � 3��2.17�2 � 2��2.17� � 1 � 7.25

y � ��2.17�2 � 3��2.17� � 4 � 7.22

x � �2.17.

��2.17, 7.25�,

y � x3 � 3x2 � 2x � 1

y � x2 � 3x � 4

Another way to approximate the points of intersectionof two graphs is to graph both equations with a graphing utility and use thezoom and trace features to find the point or points at which the two graphsintersect.

TECHNOLOGY TIP

The table shows some points onthe graphs of the equations inExample 6. You can find thepoints of intersection of thegraphs by finding the value(s) of

for which and are equal.y2y1x


−7

−7 8

8y1 = x2 − 3x − 4

y2 = x3 + 3x2 − 2x − 1

Figure B.46

6.74−2.64 −1.70

7.68

y1 = x2 − 3x − 4

y2 = x3 + 3x2 − 2x − 1

Figure B.47

If you choose to use the intersect feature of yourgraphing utility to find the point of intersection of the graphs in Example 7,you will see that it yields the same result.

TECHNOLOGY TIP

The method shown in Example 7 gives a nice graphical picture of the pointsof intersection of two graphs. However, for actual approximation purposes, it isbetter to use the algebraic procedure described in Example 6. That is, the point ofintersection of and coincides with thesolution of the equation

Equate values.

Write in general form.

By graphing with a graphing utility and using the zoomand trace features (or the zero or root feature), you can approximate the solutionof this equation to be The corresponding -value for both of thefunctions given in Example 7 is y � 7.25.

yx � �2.17.

y � x3 � 2x2 � x � 3

x3 � 2x2 � x � 3 � 0.

y- x3 � 3x2 � 2x � 1 � x2 � 3x � 4

y � x3 � 3x2 � 2x � 1y � x2 � 3x � 4

333353_APPB3.qxp 1/22/07 8:51 AM Page A53

Solving a Quadratic Equation

Method Example

Factoring: If then or

Extracting Square Roots: If where then

Completing the Square: If then

Quadratic Formula: If then

x ��b ± �b2 � 4ac

2a.

ax2 � bx � c � 0,

�x �b

2�2

� c �b2

4.

x2 � bx � �b

2�2

� c � �b

2�2

x2 � bx � c,

u � ±�c.c > 0,u2 � c,

b � 0.a � 0ab � 0,


Solving Polynomial Equations AlgebraicallyPolynomial equations can be classified by their degree. The degree of a polyno-mial equation is the highest degree of its terms. For polynomials in more than onevariable, the degree of the term is the sum of the exponents of the variables in theterm. For instance, the degree of the polynomial is 11because the sum of the exponents in the last term is the greatest.

Degree Name Example

First Linear equationSecond Quadratic equationThird Cubic equationFourth Quartic equationFifth Quintic equation

In general, the higher the degree, the more difficult it is to solve the equation—either algebraically or graphically.

You should be familiar with the following four methods for solving quadraticequations algebraically.

x5 � 12x2 � 7x � 4 � 0x4 � 3x2 � 2 � 0x3 � x � 02x2 � 5x � 3 � 06x � 2 � 4

�2x3y6 � 4xy � x7y4

x � �2 x � 2 � 0

x � 3 x � 3 � 0

�x � 3��x � 2� � 0

x2 � x � 6 � 0

or x � �7 x � 1

x � �3 ± 4

x � 3 � ±4

�x � 3�2 � 16

x � �3 ± �14

x � 3 � ±�14

�x � 3�2 � 14

x2 � 6x � 32 � 5 � 32

x2 � 6x � 5

��3 ± �17

4

x ��3 ± �32 � 4�2��1�

2�2�

2x2 � 3x � 1 � 0

The methods used to solve quadratic equations can sometimes be extendedto polynomial equations of higher degree, as shown in the next two examples.

333353_APPB3.qxp 1/22/07 8:51 AM Page A54


Example 9 Solving an Equation of Quadratic Type

Solve

SolutionThis equation is of quadratic type with To solve this equation, you can usethe Quadratic Formula.


Write in quadratic form.

Quadratic Formula

Simplify.

Solutions

Solutions

The equation has four solutions: and Checkthese solutions in the original equation. Figure B.49 verifies the solutionsgraphically.


x � ��2.x � �2,x � 1,x � �1,

x � ±1 x2 � 1

x � ±�2 x2 � 2

x2 �3 ± 1

2

x2 ��3� ± ��3�2 � 4�1��2�

2�1�

�x2�2 � 3�x2� � 2 � 0

x4 � 3x2 � 2 � 0

u � x2.

x4 � 3x2 � 2 � 0.

Example 8 Solving a Polynomial Equation by Factoring

Solve

SolutionThis equation has a common factor of 2. You can simplify the equation by firstdividing each side of the equation by 2.



Group terms.

Factor by grouping.

Set 1st factor equal to 0.

Set 2nd factor equal to 0.

The equation has three solutions: and Check thesesolutions in the original equation. Figure B.48 verifies the solutions graphically.


Occasionally, mathematical models involve equations that are of quadratictype. In general, an equation is of quadratic type if it can be written in the form

where and is an algebraic expression.ua � 0

au2 � bu � c � 0

x � ��3.x � �3,x � 3,

x � ±�3 x2 � 3 � 0

x � 3 x � 3 � 0

�x � 3��x2 � 3� � 0

x2�x � 3� � 3�x � 3� � 0

x3 � 3x2 � 3x � 9 � 0

2x3 � 6x2 � 6x � 18 � 0

2x3 � 6x2 � 6x � 18 � 0.

−1

−3 3

3y = x4 − 3x2 + 2

( )− 2, 0 2, 0( )

(−1, 0)

(1, 0)

Figure B.49

−4

−5 5

20

y = 2x3 − 6x2 − 6x + 18

( )3, 0( )− 3, 0

(3, 0)

Figure B.48

STUDY TIP

Many cubic polynomial equa-tions can be solved using factor-ing by grouping, as illustrated inExample 8.

333353_APPB3.qxp 1/22/07 8:51 AM Page A55


Set 1st factorequal to 0.Set 2nd factorequal to 0.

Write originalequation.

Square eachside.

Write ingeneral form.

Other Types of EquationsAn equation involving a radical expression can often be cleared of radicals byraising each side of the equation to an appropriate power. When using this proce-dure, it is crucial to check for extraneous solutions because of the restricteddomain of a radical equation.

Example 10 Solving an Equation Involving a Radical

Solve �2x � 7 � x � 2.

Algebraic Solution

Isolate radical.

Factor.

By substituting into the original equation, you can deter-mine that is extraneous, whereas is valid.So, the equation has only one real solution:


x � 1.x � 1x � �3

x � 1 x � 1 � 0

x � �3 x � 3 � 0

�x � 3�(x � 1� � 0

x2 � 2x � 3 � 0

2x � 7 � x2 � 4x � 4

�2x � 7 � x � 2

�2x � 7 � x � 2

Graphical SolutionFirst rewrite the equation as Thenuse a graphing utility to graph asshown in Figure B.50. Notice that the domain is because the expression under the radical cannot be nega-tive. There appears to be one solution near Use thezoom and trace features, as shown in Figure B.51, toapproximate the only solution to be .


x � 1

x � 1.

x ≥ �72

y � �2x � 7 � x � 2,�2x � 7 � x � 2 � 0.

Example 11 Solving an Equation Involving Two Radicals

Original equation

Isolate

Square each side.

Isolate

Square each side.


Factor.



By substituting into the original equation, you can determine that isextraneous, whereas is valid. Figure B.52 verifies that is the onlysolution.


x � 5x � 5x � �3

x � �3 x � 3 � 0

x � 5 x � 5 � 0

�x � 5��x � 3� � 0

x2 � 2x � 15 � 0

x2 � 2x � 1 � 4�x � 4�

2�x � 4. x � 1 � 2�x � 4

2x � 6 � 1 � 2�x � 4 � �x � 4�

�2x � 6. �2x � 6 � 1 � �x � 4

�2x � 6 � �x � 4 � 1

−4

−6 6

4

y x x= 2 + 7 2− −

−0.01

0.99 1.02

0.01

−3

−4 8

2

(5, 0)

y x x= 2 + 6 + 4 1− −

Figure B.52

333353_APPB3.qxp 1/22/07 8:51 AM Page A56


As demonstrated in Example 1, you can solve an equation involving fractionsalgebraically by multiplying each side of the equation by the least commondenominator of all terms in the equation to clear the equation of fractions.

Example 12 Solving an Equation with Rational Exponents

Solve �x � 1�2�3 � 4.

Algebraic SolutionWrite original equation.

Rewrite in radical form.

Cube each side.

Take square root of each side.

Subtract 1 from each side.

Substitute and into the original equation todetermine that both are valid solutions.


x � �9x � 7

x � 7, x � �9

x � 1 � ±8

�x � 1�2 � 64

3��x � 1�2 � 4

�x � 1�2�3 � 4

Graphical SolutionUse a graphing utility to graph and

in the same viewing window. Use the intersectfeature of the graphing utility to approximate the solu-tions to be and as shown in Figure B.53.

Figure B.53

−5

−14 13

13

(7, 4)(−9, 4)

y1 = (x + 1)23

y2 = 4

x � 7,x � �9

y2 � 4y1 � 3��x � 1�2

Example 13 Solving an Equation Involving Fractions

Solve

SolutionFor this equation, the least common denominator of the three terms is so you can begin by multiplying each term of the equation by this expression.


Simplify.


Factor.



The equation has two solutions: and Check these solutions in theoriginal equation. Use a graphing utility to verify these solutions graphically.


x � �1.x � 4

x � �1 x � 1 � 0

x � 4 x � 4 � 0

�x � 4��x � 1� � 0

x2 � 3x � 4 � 0

x � 0, 2 2�x � 2� � 3x � x�x � 2�,

x�x � 2� 2

x� x�x � 2�

3

x � 2� x�x � 2��1�

2

x�

3

x � 2� 1

x�x � 2�,

2

x�

3

x � 2� 1.

Multiply each term bythe LCD.

Graphs of functions involvingvariable denominators can betricky because graphing utilitiesskip over points at which thedenominator is zero. Graphs ofsuch functions are introduced inSections 2.6 and 2.7.


333353_APPB3.qxp 1/22/07 8:51 AM Page A57


Example 14 Solving an Equation Involving Absolute Value

Solve

SolutionBegin by writing the equation as From the graph of

in Figure B.54, you can estimate the solutions to beand These solutions can be verified by substitution into the

equation. To solve an equation involving absolute value algebraically, you mustconsider the fact that the expression inside the absolute value symbols can bepositive or negative. This results in two separate equations, each of which mustbe solved.

First Equation:

Use positive expression.


Factor.



Second Equation:

Use negative expression.


Factor.



Check

Substitute for

checks. ✓

Substitute 2 for

2 does not check.

Substitute 1 for

1 checks. ✓

Substitute 6 for

6 does not check.

The equation has only two solutions: and just as you obtained by graphing.


x � 1,x � �3

18 � �18

x. 62 � 3�6� �?

�4�6� � 6

2 � 2

x. 12 � 3�1� �?

�4�1� � 6

2 � �2

x. 22 � 3�2� �?

�4�2� � 6

�3 18 � 18

x.�3 ��3�2 � 3��3� �?

�4��3� � 6

x � 6 x � 6 � 0

x � 1 x � 1 � 0

�x � 1��x � 6� � 0

x2 � 7x � 6 � 0

��x2 � 3x� � �4x � 6

x � 2 x � 2 � 0

x � �3 x � 3 � 0

�x � 3��x � 2� � 0

x2 � x � 6 � 0

x2 � 3x � �4x � 6

x � 1.x � �3y � x2 � 3x � 4x � 6

x2 � 3x � 4x � 6 � 0.

x2 � 3x � �4x � 6.

−7

−8 7

3

(1, 0)(−3, 0)

y =⏐x2 − 3x⏐+ 4x − 6

Figure B.54

333353_APPB3.qxp 1/22/07 8:51 AM Page A58


In Exercises 1–6, determine whether each value of x is asolution of the equation.

Equation Values

1. (a) (b)

(c) (d)

2. (a) (b)

(c) (d)

3. (a) (b)

(c) (d)

4. (a) (b)

(c) (d)

5. (a) (b)

(c) (d)

6. (a) (b)

(c) (d)

In Exercises 7–12, determine whether the equation is anidentity or a conditional equation.

7.

8.

9.

10.

11. 12.

In Exercises 13–16, solve the equation using two methods.Then decide which method is easier and explain why.

13. 14.

15. 16.

In Exercises 17– 40, solve the equation (if possible). Use agraphing utility to verify your solution.

17. 18.

19. 20.

21. 22.

23. 24.

25. 26.

27. 28.

29. 30.

31. 32.

33.

34.

35.

36.x

x � 4�

4

x � 4� 2 � 0

7

2x � 1�

8x

2x � 1� �4

1

x � 2�

3

x � 3�

4

x2 � x � 6

1

x � 3�

1

x � 3�

10

x2 � 9

10x � 3

5x � 6�

1

2

5x � 4

5x � 4�

2

3

17 � y

y�

32 � y

y� 100

100 � 4u

3�

5u � 6

4� 6

53

� 2�y � 1� �103

2�z � 4�5

� 5 � 10z

3x

2�

1

4�x � 2� � 10

3

2�z � 5� �

1

4�z � 24� � 0

5x

4�

1

2� x �

1

2

x

5�

x

2� 3

5�z � 4� � 4z � 5 � 6z3�y � 5� � 3 � 5y

5y � 1 � 8y � 5 � 6y4y � 2 � 5y � 7 � 6y

5x � 3 � 6 � 2x3x � 5 � 2x � 7

4y3

� 2y �165

2x5

� 5x �43

3z8

�z

10� 6

3x8

�4x3

� 4

5

x�

3

x� 243 �

1

x � 1�

4x

x � 1

x2 � 2�3x � 2� � x2 � 6x � 4

x2 � 8x � 5 � �x � 4�2 � 11

�7�x � 3� � 4x � 3�7 � x�2�x � 1� � 2x � 2

x � 16x � 9

x � 0x � �163�x � 8

3� �

23

x � 32x � 21

x � 0x � �3�x � 4

6� 3 � 4

x � 9x � 7

x � �2x � �3�x � 5��x � 3�

2� 24

x � 5x � 0

x � �2x � �13 �1

x � 2� 4

x � 7x �12

x � 1x � �2x2

�6x7

�1914

x �14x � 0

x � 4x � �12

5

2x�

4

x� 3


Vocabulary Check

Fill in the blanks.

1. An _______ is a statement that equates two algebraic expressions.

2. To find all values that satisfy an equation is to _______ the equation.

3. When solving an equation, it is possible to introduce an _______ solution, which is a value that does not satisfy the original equation.

4. The points and are called the _______ and _______ respectively, of the graph of an equation.

5. An ordered pair that is a solution of two different equations is called a _______ of the graphs of the two equations.

�0, b��a, 0�

333353_APPB3.qxp 1/22/07 8:51 AM Page A59


37. 38.

39. 40.

In Exercises 41–52, use a graphing utility to find the andintercepts of the graph of the equation.

41. 42.

43. 44.

45. 46.

47. 48.

49. 50.

51. 52.

Graphical Analysis In Exercises 53–56, use a graphingutility to graph the equation and approximate any inter-cepts. Set and solve the resulting equation. Comparethe results with the intercepts of the graph.

53. 54.

55. 56.

In Exercises 57–62, the solution(s) of the equation are given.Verify the solution(s) both algebraically and graphically.

Equation Solution(s)

57.

58.

59.

60.

61.

62.

In Exercises 63–86, solve the equation algebraically. Thenverify your algebraic solution by writing the equation in theform and using a graphing utility to graph theequation.

63. 64.

65.

66.

67. 68.

69.

70.

71. 72.

73. 74.

75.

76.

77.

78.

79.

80.

81. 82.

83. 84.

85. 86.

In Exercises 87–92, determine any point(s) of intersection ofthe equations algebraically. Then use a graphing utility toverify your results.

87. 88.

89. 90.

91. 92.

−8

−4 14

4 y = −x2 + 3x + 1

y = −x2 − 2x − 4−3

−6 12

9 y = x2 + 2x + 4

y = x2 − x + 1

y � �x2 � 2x � 4y � x2 � 2x � 4

y � �x2 � 3x � 1y � x2 � x � 1

−4

−7 7

10x3 + y = 0 3x + y = 2

−1

−6 6

7x2 − y = −2 x − y = −4

x3 � y � 0 x2 � y � �2

3x � y � 2 x � y � �4

−1

−6 6

7 x − y = −4x + 2y = 5

−4

−6 6

4y = 2x − 1y = 2 − x

x � 2y � 5y � 2x � 1

x � y � �4y � 2 � x

�x � 4 � 8�x � 2 � 3x � 1 � 6x � 3 � 4

5

x� 1 �

3

x � 2

2

x � 2� 3

5 � 3x1�3 � 2x2�3

x4 � 2x2 � 1

4x3 � 12x2 � 8x � 24 � 0

2x3 � x 2 � 18x � 9 � 0

�x � 1�2 � 2�x � 2� � �x � 1��x � 2��x � 2�2 � x2 � 6x � 1

6

x�

8

x � 5� 3

3

x � 2�

4

x � 2� 5

x � 3

25�

x � 5

12

2x

3� 10 �

24

x

0.75x � 0.2�80 � x� � 20

0.60x � 0.40�100 � x� � 1.2

2x3

�12

�x � 5� � 63x

2�

1

4�x � 2� � 10

1200 � 300 � 2�x � 500�25�x � 3� � 12�x � 2� � 10

3.5x � 8 � 0.5x2.7x � 0.4x � 1.2

y � 0

x � �2, 5y � x � 3 �10

x

x � 1y �x � 2

3�

x � 1

5� 1

x � 0, 3, 6y � x3 � 9x 2 � 18x

x � 0, 5, 1y � x3 � 6x2 � 5x

x � 2y � 3�x � 5� � 9

x � 4y � 5�4 � x�

y � 10 � 2�x � 2�y � 20 � �3x � 10�y � 4�x � 3� � 2y � 2�x � 1� � 4

x-y � 0

x-

xy � x � 4y � 0xy � 2y � x � 1 � 0

y � 3 �12x � 1y � x � 2 � 4

y �3x � 1

4xy �

4x

y � �12x�x � 3 � 1y � x�x � 2

y � 4 � x 2y � x 2 � x � 2

y � �34x � 3y � x � 5

y-x-

6

x�

2

x � 3�

3�x � 5�x�x � 3�

3

x2 � 3x�

4

x�

1

x � 3

3 � 2 �2

z � 2

1

x�

2

x � 5� 0

333353_APPB3.qxp 1/22/07 8:52 AM Page A60


In Exercises 93–98, use a graphing utility to approximateany points of intersection (accurate to three decimal places)of the graphs of the equations. Verify your resultsalgebraically.

93. 94.

95. 96.

97. 98.

In Exercises 99–108, solve the quadratic equation by factor-ing. Check your solutions in the original equation.

99. 100.

101. 102.

103. 104.

105. 106.

107. 108.

In Exercises 109–118, solve the equation by extractingsquare roots. List both the exact solutions and the decimalsolutions rounded to two decimal places.

109. 110.

111. 112.

113. 114.

115. 116.

117. 118.

In Exercises 119–128, solve the quadratic equation by com-pleting the square. Verify your answer graphically.

119. 120.

121. 122.

123. 124.

125. 126.

127. 128.

In Exercises 129–138, use the Quadratic Formula to solvethe equation. Use a graphing utility to verify your solutionsgraphically.

129. 130.

131. 132.

133. 134.

135. 136.

137. 138.

In Exercises 139–148, solve the equation using anyconvenient method. Use a graphing utility to verify yoursolutions graphically.

139. 140.

141. 142.

143. 144.

145. 146.

147. 148.

In Exercises 149–166, find all solutions of the equationalgebraically. Use a graphing utility to verify the solutionsgraphically.

149. 150.

151. 152.

153. 154.

155. 156.

157.

158.

159. 160.

161. 162.

163.

164.

165. 166.

In Exercises 167–186, find all solutions of the equationalgebraically. Check your solutions both algebraically andgraphically.

167. 168.

169. 170.

171. 172.

173. 174.

175. 176.

177.

178.

179. 180.

181. 182.

183. 184.

185. 186. x � 10 � x 2 � 10xx � x2 � x � 33x � 2 � 72x � 1 � 5

4x � 1 �3

xx �

3

x�

1

2

x

x 2 � 4�

1

x � 2� 3

1

x�

1

x � 1� 3

4x2�x � 1�1�3 � 6x�x � 1�4�3 � 0

3x�x � 1�1�2 � 2�x � 1�3�2 � 0

�x2 � x � 22�4�3 � 16�x � 5�2�3 � 16

�x ��x � 20 � 10�x � �x � 5 � 1

3�4x � 3 � 2 � 03�2x � 1 � 8 � 0

�x � 5 � 2x � 3�x � 1 � 3x � 1

�2x � 5 � 3 � 0�x � 10 � 4 � 0

6x � 7�x � 3 � 02x � 9�x � 5 � 0

8� tt � 1�

2

� 2� tt � 1� � 3 � 0

6� s

s � 1�2

� 5� s

s � 1� � 6 � 0

6 �1x

�1x2 � 0

1

t 2�

8

t� 15 � 0

36t 4 � 29t 2 � 7 � 04x 4 � 65x 2 � 16 � 0

x 4 � 2x3 � 8x � 16 � 0

x3 � 3x 2 � x � 3 � 0

x 4 � 5x2 � 36 � 0x 4 � 4x2 � 3 � 0

20x3 � 125x � 04x4 � 18x2 � 0

9x 4 � 24x3 � 16x 2 � 05x3 � 30x 2 � 45x � 0

8x4 � 18x2 � 04x4 � 16x2 � 0

a � 0a2x2 � b2 � 0,�x � 1�2 � x2

x2 � 3x �34 � 0x2 � x �

114 � 0

x2 � 2x �134 � 0x2 � 14x � 49 � 0

�x � 1�2 � �1�x � 3�2 � 81

11x2 � 33x � 0x2 � 2x � 1 � 0

9x2 � 6x � 37 � 03x2 � 16x � 17 � 0

9x2 � 24x � 16 � 028x � 49x 2 � 4

x2 � 16 � �5xx2 � 3x � �8

4x 2 � 4x � 4 � 0x 2 � 8x � 4 � 0

x 2 � 10x � 22 � 02 � 2x � x 2 � 0

9x2 � 12x � 14 � 02x2 � 5x � 8 � 0

�x2 � x � 1 � 0�6 � 2x � x2 � 0

4x2 � 4x � 99 � 09x2 � 18x � 3 � 0

x 2 � 8x � 14 � 0x 2 � 6x � 2 � 0

x2 � 2x � 3 � 0x2 � 4x � 32 � 0

�x � 5�2 � �x � 4�2�x � 7�2 � �x � 3�2

�4x � 7�2 � 44�2x � 1�2 � 12

�2x � 3�2 � 25 � 0�3x � 1)2 � 6 � 0

�x � 5�2 � 25�x � 12�2 � 16

x2 � 144x 2 � 49

x2 � 2ax � a2 � 0�x � a�2 � b 2 � 0

�x2 � 8x � 12x 2 � 4x � 12

2x 2 � 19x � 333 � 5x � 2x 2 � 0

x 2 � 10x � 9 � 0x 2 � 2x � 8 � 0

9x 2 � 1 � 06x 2 � 3x � 0

y � 2x � x 2y � x 4 � 2x 2

y � �xy � 2x 2

y � 5 � 2xy � 2x � 1

y � x 3 � 3y � 4 � x 2

y �52x � 11y � x � 3

y �13x � 2y � 9 � 2x

333353_APPB3.qxp 1/22/07 8:52 AM Page A61


Graphical Analysis In Exercises 187–194, (a) use a graph-ing utility to graph the equation, (b) use the graph to approx-imate any x-intercepts of the graph, (c) set and solvethe resulting equation, and (d) compare the result of part (c)with the x-intercepts of the graph.

187. 188.

189. 190.

191. 192.

193. 194.

195. State Populations The populations (in thousands) ofSouth Carolina and Arizona from 1980 to 2004 canbe modeled by

where represents the year, with corresponding to1980. (Source: U.S. Census Bureau)

(a) Use a graphing utility to graph each model in the sameviewing window over the appropriate domain.Approximate the point of intersection. Round yourresult to one decimal place. Explain the meaning ofthe coordinates of the point.

(b) Find the point of intersection algebraically. Roundyour result to one decimal place. What does the pointof intersection represent?

(c) Explain the meaning of the slopes of both models andwhat it tells you about the population growth rates.

(d) Use the models to estimate the population of each statein 2010. Do the values seem reasonable? Explain.

196. Medical Costs The average retail prescription prices P(in dollars) from 1997 through 2004 can be approximatedby the model

where represents the year, with corresponding to1997. (Source: National Association of Chain DrugStores)

(a) Determine algebraically when the average retail pricewas $40 and $50.

(b) Verify your answer to part (a) by creating a table ofvalues for the model.

(c) Use a graphing utility to graph the model.

(d) According to the model, when will the average retailprice reach $75?

(e) Do you believe the model could be used to predict theaverage retail prices for years beyond 2004? Explainyour reasoning.

197. Biology The metabolic rate of an ectothermic organismincreases with increasing temperature within a certainrange. Experimental data for oxygen consumption C (inmicroliters per gram per hour) of a beetle at certaintemperatures yielded the model

where is the air temperature in degrees Celsius.

(a) Use a graphing utility to graph the consumptionmodel over the specified domain.

(b) Use the graph to approximate the air temperatureresulting in oxygen consumption of 150 microlitersper gram per hour.

(c) The temperature is increased from to . Theoxygen consumption is increased by approximatelywhat factor?

198. Saturated Steam The temperature (in degreesFahrenheit) of saturated steam increases as pressureincreases. This relationship is approximated by

where is the absolute pressure in pounds per square inch.

(a) Use a graphing utility to graph the model over thespecified domain.

(b) The temperature of steam at sea level isF. Evaluate the model at this pressure and verify

the result graphically.

(c) Use the model to approximate the pressure for a steamtemperature of F.

Synthesis

True or False? In Exercises 199 and 200, determinewhether the statement is true or false. Justify your answer.

199. Two linear equations can have either one point ofintersection or no points of intersection.

200. An equation can never have more than one extraneoussolution.

201. Think About It Find c such that is a solution tothe linear equation

202. Think About It Find c such that is a solution tothe linear equation

203. Exploration Given that and are nonzero realnumbers, determine the solutions of the equations.

(a) (b) ax 2 � ax � 0ax 2 � bx � 0

ba

5x � 2c � 12 � 4x � 2c.x � 2

2x � 5c � 10 � 3c � 3x.x � 3

240�

212��x � 14.696�

x

5 ≤ x ≤ 40T � 75.82 � 2.11x � 43.51�x,

T

20�C10�C

x

10 ≤ x ≤ 25C � 0.45x2 � 1.65x � 50.75,

t � 7t

7 ≤ t ≤ 14P � 0.1220t2 � 1.529t � 18.72,

t � 0t

0 ≤ t ≤ 24A � 128.2t � 2533,

0 ≤ t ≤ 24S � 45.2t � 3087,

A,S,

y � x � 2 � 3y � x � 1 � 2

y � x �9

x � 1� 5y �

1x

�4

x � 1� 1

y � 2x � �15 � 4xy � �11x � 30 � x

y � x4 � 10x2 � 9y � x3 � 2x2 � 3x

y � 0

333353_APPB3.qxp 1/22/07 8:52 AM Page A62

B.4 Solving Inequalities Algebraically and Graphically

What you should learn� Use properties of inequalities to solve

linear inequalities.

� Solve inequalities involving absolute

values.

� Solve polynomial inequalities.

� Solve rational inequalities.

� Use inequalities to model and solve

real-life problems.

Why you should learn itAn inequality can be used to determine

when a real-life quantity exceeds a given

level. For instance, Exercises 85–88 on page

A74 show how to use linear inequalities to

determine when the number of hours per

person spent playing video games exceeded

the number of hours per person spent

reading newspapers.

Appendix B.4 Solving Inequalities Algebraically and Graphically A63

Properties of InequalitiesThe inequality symbols and were used to compare two numbers and todenote subsets of real numbers. For instance, the simple inequality denotes all real numbers that are greater than or equal to 3.

In this section, you will study inequalities that contain more involved state-ments such as

and

As with an equation, you solve an inequality in the variable by finding allvalues of for which the inequality is true. These values are solutions of theinequality and are said to satisfy the inequality. For instance, the number 9 is asolution of the first inequality listed above because

On the other hand, the number 7 is not a solution because

The set of all real numbers that are solutions of an inequality is the solution setof the inequality.

The set of all points on the real number line that represent the solution set isthe graph of the inequality. Graphs of many types of inequalities consist ofintervals on the real number line.

The procedures for solving linear inequalities in one variable are much like those for solving linear equations. To isolate the variable, you can make useof the properties of inequalities. These properties are similar to the propertiesof equality, but there are two important exceptions. When each side of aninequality is multiplied or divided by a negative number, the direction of theinequality symbol must be reversed in order to maintain a true statement. Here isan example.

Original inequality

Multiply each side by and reverse the inequality.

Simplify.

Two inequalities that have the same solution set are equivalent inequalities. Forinstance, the inequalities

and

are equivalent. To obtain the second inequality from the first, you can subtract 2from each side of the inequality. The properties listed at the top of the next pagedescribe operations that can be used to create equivalent inequalities.

x < 3x � 2 < 5

6 > �15

�3 ��3��2� > ��3��5�

�2 < 5

28 >� 30.

5�7� � 7 >� 3�7� � 9

38 > 36.

5�9� � 7 > 3�9� � 9

xx

�3 ≤ 6x � 1 < 3.5x � 7 > 3x � 9

xx ≥ 3

≥>,≤,<,

Prerequisite Skills

To review techniques for solving

linear inequalities, see Appendix E.

333353_APPB4.qxp 1/22/07 8:54 AM Page A63


x

6 7 8 9 10

Figure B.55 Solution Interval: �8, ��

Properties of Inequalities

Let and be real numbers.

1. Transitive Property

and

2. Addition of Inequalities

and

3. Addition of a Constant

4. Multiplying by a Constant

For

For ac > bcc < 0, a < b

ac < bcc > 0, a < b

a � c < b � ca < b

a � c < b � dc < da < b

a < cb < ca < b

da, b, c,

E x p l o r a t i o nUse a graphing utility to graph and

in the sameviewing window. (Use

and) For which

values of does the graph of lie above the graph of

Explain how the answer to thisquestion can be used to solvethe inequality in Example 1.

g?fx

�5 ≤ y ≤ 50.�1 ≤ x ≤ 15

g�x� � 3x � 9f �x� � 5x � 7

STUDY TIP

Checking the solution set of aninequality is not as simple aschecking the solution(s) of anequation because there aresimply too many -values tosubstitute into the originalinequality. However, you can get an indication of the validity of the solution set bysubstituting a few convenientvalues of For instance, inExample 1, try substituting

and into theoriginal inequality.

x � 10x � 5

x.

x

Each of the properties above is true if the symbol is replaced by and isreplaced by For instance, another form of Property 3 is as follows.

Solving a Linear InequalityThe simplest type of inequality to solve is a linear inequality in one variable,such as (See Appendix E for help with solving one-step linearinequalities.)

2x � 3 > 4.

a � c ≤ b � ca ≤ b

≥.>≤<

Example 1 Solving a Linear Inequality

Solve

SolutionWrite original inequality.


Add 7 to each side.


So, the solution set is all real numbers that are greater than 8. The intervalnotation for this solution set is The number line graph of this solution setis shown in Figure B.55. Note that a parenthesis at 8 on the number line indicatesthat 8 is not part of the solution set.


Note that the four inequalities forming the solution steps of Example 1 areall equivalent in the sense that each has the same solution set.

�8, ��.

x > 8

2x > 16

3x 2x � 7 > 9

5x � 7 > 3x � 9

5x � 7 > 3x � 9.

333353_APPB4.qxp 1/22/07 8:54 AM Page A64


Example 2 Solving an Inequality

Solve 1 �32x ≥ x � 4.

Algebraic SolutionWrite original inequality.

Multiply each side by the LCD.


Subtract 2 from each side.

The solution set is all real numbers that are less than orequal to 2. The interval notation for this solution set is

The number line graph of this solution set isshown in Figure B.56. Note that a bracket at 2 on thenumber line indicates that 2 is part of the solution set.

Figure B.56 Solution Interval:


��, 2]

x

0 1 2 3 4

��, 2�.

x ≤ 2

�5x ≥ �10

2x 2 � 5x ≥ �8

2 � 3x ≥ 2x � 8

1 �32x ≥ x � 4

Graphical SolutionUse a graphing utility to graph and

in the same viewing window. In Figure B.57,you can see that the graphs appear to intersect at the point

Use the intersect feature of the graphing utility toconfirm this. The graph of lies above the graph of tothe left of their point of intersection, which implies that

for all

Figure B.57

−5

−6

2

7

y2 = x − 4

y1 = 1 − x 32

x ≤ 2.y1 ≥ y2

y2y1

�2, �2�.

y2 � x � 4y1 � 1 �

32x

Example 3 Solving a Double Inequality

Solve and 6x � 1 < 3.�3 ≤ 6x � 1

Algebraic SolutionWrite as a double inequality.

Add 1 to each part.

Divide by 6 and simplify.

The solution set is all real numbers that are greater than or

equal to and less than The interval notation for this

solution set is The number line graph of this

solution set is shown in Figure B.58.

Figure B.58 Solution Interval:


[�13, 23�

x

−1 0 1

− 13

23

��13, 23�.

23.�

13

�13 ≤ x < 2

3

�2 ≤ 6x < 4

�3 ≤ 6x � 1 < 3

Graphical Solution


and in the same viewing window. In Figure B.59,

you can see that the graphs appear to intersect at the points

and Use the intersect feature of the

graphing utility to confirm this. The graph of lies above

the graph of to the right of and the graph of

lies below the graph of to the left of This

implies that when

Figure B.59

−8

−5

5

7

y1 = 6x − 1

y2 = −3

y3 = 3

�13 ≤ x < 2

3.y2 ≤ y1 < y3

�23, 3�.y3y1

��13, �3�y2

y1

�23, 3�.��1

3, �3�

y3 � 3

y2 � �3,y1 � 6x � 1,

Divide each side by andreverse the inequality.

�5

Sometimes it is possible to write two inequalities as a double inequality, asdemonstrated in Example 3.

333353_APPB4.qxp 1/22/07 8:54 AM Page A65


Inequalities Involving Absolute Values

Solving an Absolute Value Inequality

Let be a variable or an algebraic expression and let be a real number such that

1. The solutions of are all values of that lie between and

if and only if Double inequality

2. The solutions of are all values of that are less than or greater than

if and only if or Compound inequality

These rules are also valid if is replaced by and is replaced by ≥.>≤<

x > a.x < �a�x� > a

a.�ax�x� > a

�a < x < a.�x� < a

a.�ax�x� < a

a ≥ 0.ax

Example 4 Solving Absolute Value Inequalities

Solve each inequality.

a. b. �x � 5� > 2�x � 5� < 2

Graphical Solutiona. Use a graphing utility to graph

and in the same viewing window. InFigure B.62, you can see that the graphsappear to intersect at the points and

Use the intersect feature of thegraphing utility to confirm this. The graphof lies below the graph of when

So, you can approximate thesolution set to be all real numbers greaterthan 3 and less than 7.

Figure B.62

b. In Figure B.62, you can see that the graphof lies above the graph of when or when So, you can approximatethe solution set to be all real numbers thatare less than 3 or greater than 7.

x > 7.x < 3y2y1

−2

−3

5

10

y2 = 2 y1 = ⏐x − 5⏐

3 < x < 7.y2y1

�7, 2�.�3, 2�

y2 � 2y1 � �x � 5�

Algebraic Solutiona. Write original inequality.

Write double inequality.

Add 5 to each part.

The solution set is all real numbers that are greater than 3 and lessthan 7. The interval notation for this solution set is Thenumber line graph of this solution set is shown in Figure B.60.

b. The absolute value inequality is equivalent to the following compound inequality: or

Solve first inequality: Write first inequality.

Add 5 to each side.

Solve second inequality: Write second inequality.

Add 5 to each side.

The solution set is all real numbers that are less than 3 or greaterthan 7. The interval notation for this solution set is

The symbol is called a union symbol and isused to denote the combining of two sets. The number line graph ofthis solution set is shown in Figure B.61.



x2 3 4 5 6 7 8

2 units 2 units

x2 3 4 5 6 7 8

2 units 2 units

��, 3� � �7, ��.

x > 7

x � 5 > 2

x < 3

x � 5 < �2

x � 5 > 2.x � 5 < �2�x � 5� > 2

�3, 7�.

3 < x < 7

�2 < x � 5 < 2

�x � 5� < 2

333353_APPB4.qxp 1/22/07 8:54 AM Page A66


Polynomial InequalitiesTo solve a polynomial inequality such as use the fact that apolynomial can change signs only at its zeros (the x-values that make thepolynomial equal to zero). Between two consecutive zeros, a polynomial must beentirely positive or entirely negative. This means that when the real zeros of apolynomial are put in order, they divide the real number line into intervals inwhich the polynomial has no sign changes. These zeros are the critical numbersof the inequality, and the resulting open intervals are the test intervals for theinequality. For instance, the polynomial above factors as

and has two zeros, and which divide the real number line intothree test intervals: and To solve the inequality

you need to test only one value in each test interval.x2 � 2x � 3 < 0,�3, ��.��1, 3�,��, �1�,

x � 3,x � �1

x2 � 2x � 3 � �x � 1��x � 3�

x2 � 2x � 3 < 0,

−4

−4 5

2

y = x2 − 3

Figure B.63

Finding Test Intervals for a Polynomial

To determine the intervals on which the values of a polynomial are entirelynegative or entirely positive, use the following steps.

1. Find all real zeros of the polynomial, and arrange the zeros inincreasing order. The zeros of a polynomial are its critical numbers.

2. Use the critical numbers to determine the test intervals.

3. Choose one representative value in each test interval and evaluatethe polynomial at that value. If the value of the polynomial is nega-tive, the polynomial will have negative values for every value in theinterval. If the value of the polynomial is positive, the polynomialwill have positive values for every x-value in the interval.

x-

x-

Example 5 Investigating Polynomial Behavior

To determine the intervals on which is entirely negative and those on whichit is entirely positive, factor the quadratic as Thecritical numbers occur at and So, the test intervals for thequadratic are and In each test interval,choose a representative -value and evaluate the polynomial, as shown in the table.

The polynomial has negative values for every in the interval andpositive values for every in the intervals and This resultis shown graphically in Figure B.63.


�3, ��.��, �3�x��3, 3�x

x�3, ��.��3, 3�,��, �3�,

x � 3.x � �3x2 � 3 � �x � 3��x � 3�.

x2 � 3

Some graphing utilities willproduce graphs of inequalities.For instance, you can graph

by setting thegraphing utility to dot mode andentering Using the settings and your graphshould look like the graph shownbelow. Solve the problemalgebraically to verify that thesolution is

−10

−4

4

10

y = 2x2 + 5x > 12

��, �4� � �32, ��.

�4 ≤ y ≤ 4,�10 ≤ x ≤ 10

y � 2x2 � 5x > 12.

2x2 � 5x > 12


Interval x-Value Value of Polynomial Sign of Polynomial

��, �3 � x � �3 ��3�2 � 3 � 6 Positive

��3, 3� x � 0 �0�2 � 3 � �3 Negative

�3, �� x � 5 �5�2 � 3 � 22 Positive

333353_APPB4.qxp 1/22/07 8:54 AM Page A67


To determine the test intervals for a polynomial inequality, the inequalitymust first be written in general form with the polynomial on one side.

Example 6 Solving a Polynomial Inequality

Solve 2x2 � 5x > 12.

Algebraic SolutionWrite inequality in general form.

Factor.

Critical Numbers:

Test Intervals:

Test: Is

After testing these intervals, you can see that the polynomialis positive on the open intervals

and Therefore, the solution set of the inequality is


��, �4� � �32, ��.

� 32, ��.

��, �4�2x2 � 5x � 12

�x � 4��2x � 3� > 0?

��, �4�, ��4, 32�, �32, ��

x � �4, x �32

�x � 4��2x � 3� > 0

2x2 � 5x � 12 > 0

Graphical SolutionFirst write the polynomial inequality as

Then use a graphing utility tograph In Figure B.64, you can seethat the graph is above the axis when is less than

or when is greater than So, you can graphicallyapproximate the solution set to be

Figure B.64

−7

−16

5

y = 2x2 + 5x − 12

(−4, 0)32, 0( (

4

��, �4� � �32, ��.

32.x�4

xx-y � 2x2 � 5x � 12.

2x2 � 5x � 12 > 0.2x2 � 5x > 12

STUDY TIP

When solving a quadraticinequality, be sure you haveaccounted for the particular typeof inequality symbol given inthe inequality. For instance,in Example 7, note that the original inequality contained a “greater than” symbol and the solution consisted of twoopen intervals. If the originalinequality had been

the solution would haveconsisted of the closed interval

and the interval �4, ��.��4, 32 �

2x3 � 3x2 � 32x ≥ �48

Example 7 Solving a Polynomial Inequality

Solve

SolutionWrite inequality in general form.

Factor by grouping.

Distributive Property

Factor difference of two squares.

The critical numbers are and and the test intervals are

and

Interval x-Value Polynomial Value Conclusion

Negative

Positive

Negative

Positive

From this you can conclude that the polynomial is positive on the open intervalsand So, the solution set is


��4, 32� � �4, ��.�4, ��.��4, 32�

2�5�3 � 3�5�2 � 32�5� � 48 � 63x � 5�4, ��

2�2�3 � 3�2�2 � 32�2� � 48 � �12x � 2�32, 4�

2�0�3 � 3�0�2 � 32�0� � 48 � 48x � 0��4, 32�2��5�3 � 3��5�2 � 32��5� � 48 � �117x � �5��, �4�

�4, ��.��, �4�, ��4, 32�, �32, 4�,

x � 4;x � �4, x �32,

�x � 4��x � 4��2x � 3� > 0

�x2 � 16��2x � 3� > 0

x2�2x � 3� � 16�2x � 3� > 0

2x3 � 3x2 � 32x � 48 > 0

2x3 � 3x2 � 32x > �48.

333353_APPB4.qxp 1/22/07 8:54 AM Page A68


Example 8 Unusual Solution Sets

a. The solution set of

consists of the entire set of real numbers, In other words, the valueof the quadratic is positive for every real value of as indicatedin Figure B.65(a). (Note that this quadratic inequality has no critical numbers.In such a case, there is only one test interval—the entire real number line.)

b. The solution set of

consists of the single real number because the quadratic has one critical number, and it is the only value that satisfies theinequality, as indicated in Figure B.65(b).

c. The solution set of

is empty. In other words, the quadratic is not less than zero forany value of as indicated in Figure B.65(c).

d. The solution set of

consists of all real numbers except the number 2. In interval notation, thissolution set can be written as The graph of lies above the axis except at where it touches it, as indicated in FigureB.65(d).

(a) (b)

(c) (d)

Figure B.65


−3

−1

6

y = x2 − 4x + 45

(2, 0)−7

−1

5

y = x2 + 3x + 57

−5

−1

4

y = x2 + 2x + 15

(−1, 0)−6

−1

6

y = x2 + 2x + 47

x � 2,x-x2 � 4x � 4��, 2� � �2, ��.

x2 � 4x � 4 > 0

x,x2 � 3x � 5

x2 � 3x � 5 < 0

x � �1,x2 � 2x � 1�1�,

x2 � 2x � 1 ≤ 0

x,x2 � 2x � 4��, ��.

x2 � 2x � 4 > 0One of the advantages oftechnology is that you can solve complicated polynomialinequalities that might bedifficult, or even impossible,to factor. For instance, you could use a graphing utility toapproximate the solution to theinequality

x3 � 0.2x2 � 3.16x � 1.4 < 0.


333353_APPB4.qxp 1/22/07 8:54 AM Page A69


Rational InequalitiesThe concepts of critical numbers and test intervals can be extended to inequalitiesinvolving rational expressions. To do this, use the fact that the value of a rationalexpression can change sign only at its zeros (the -values for which its numeratoris zero) and its undefined values (the -values for which its denominator is zero).These two types of numbers make up the critical numbers of a rational inequality.

xx

Example 9 Solving a Rational Inequality

Solve 2x � 7

x � 5≤ 3.

Graphical SolutionUse a graphing utility to graph

and

in the same viewing window. In Figure B.66,you can see that the graphs appear to intersect atthe point Use the intersect feature of thegraphing utility to confirm this. The graph of lies below the graph of in the intervals

and So, you can graphicallyapproximate the solution set to be all realnumbers less than 5 or greater than or equal to 8.

Figure B.66

−3

−4

12

6y2 = 3

2x − 7x − 5

y1 =

�8, ��.��, 5�y2

y1

�8, 3�.

y2 � 3y1 �2x � 7x � 5

Algebraic Solution

Write original inequality.


Write as single fraction.

Simplify.

Now, in standard form you can see that the critical numbers areand and you can proceed as follows.

Critical Numbers:Test Intervals:

Test: Is

Interval x-Value Polynomial Value Conclusion

Negative

Positive

Negative

By testing these intervals, you can determine that the rationalexpression is negative in the open intervals

and Moreover, because when you can conclude that the solution set of the inequalityis


��, 5� � �8, ��.x � 8,

��x � 8��x � 5� � 0�8, ��.��, 5��x � 8��x � 5�

�9 � 8 9 � 5

� �14

x � 9�8, ��

�6 � 8 6 � 5

� 2x � 6�5, 8�

�0 � 8 0 � 5

� �85

x � 0��, 5�

�x � 8

x � 5≤ 0?

��, 5�, �5, 8�, �8, ��x � 5, x � 8

x � 8,x � 5

�x � 8x � 5

≤ 0

2x � 7 � 3x � 15

x � 5≤ 0

2x � 7x � 5

� 3 ≤ 0

2x � 7x � 5

≤ 3

Note in Example 9 that is not included in the solution set because theinequality is undefined when x � 5.

x � 5

333353_APPB4.qxp 1/22/07 8:54 AM Page A70


ApplicationThe implied domain of a function is the set of all -values for which the function is defined. A common type of implied domain is used to avoid even roots of negative numbers, as shown in Example 10.

x

−2

−9 9

10

(4, 0)(−4, 0)

y = 64 − 4x2

Figure B.67

00 24

3000y2 = 2000

Figure B.68

Example 10 Finding the Domain of an Expression

Find the domain of

SolutionBecause is defined only if is nonnegative, the domain isgiven by



Factor.

The inequality has two critical numbers: and A test shows thatin the closed interval The graph of

shown in Figure B.67, confirms that the domain is


��4, 4�.y � 64 � 4x2,��4, 4�.64 � 4x2

≥ 0x � 4.x � �4

�4 � x��4 � x� ≥ 0

16 � x2≥ 0

64 � 4x2≥ 0

64 � 4x2≥ 0.

64 � 4x264 � 4x2

64 � 4x2 .

Example 11 Height of a Projectile

A projectile is fired straight upward from ground level with an initial velocity of384 feet per second. During what time period will its height exceed 2000 feet?

SolutionThe position of an object moving vertically can be modeled by the position equation

where is the height in feet and is the time in seconds. In this case, andSo, you need to solve the inequality Using a

graphing utility, graph and as shown in FigureB.68. From the graph, you can determine that for between approximately 7.6 and 16.4. You can verify this result algebraically.

Write original inequality.

Divide by and reverse inequality.


By the Quadratic Formula the critical numbers are andor approximately 7.64 and 16.36. A test will verify that the

height of the projectile will exceed 2000 feet when that is,during the time interval seconds.


�7.64, 16.36�7.64 < t < 16.36;

t � 12 � 19,t � 12 � 19

t2 � 24t � 125 < 0

�16 t2 � 24t < �125

�16t2 � 384t > 2000

t�16t2 � 384t > 2000y2 � 2000,y1 � �16t2 � 384t

�16t2 � 384t > 2000.v0 � 384.s0 � 0ts

s � �16t2 � v0 t � s0

333353_APPB4.qxp 1/22/07 8:54 AM Page A71


In Exercises 1–6, match the inequality with its graph. [Thegraphs are labeled (a), (b), (c), (d), (e), and (f).]

(a)

(b)

(c)

(d)

(e)

(f )

1. 2.

3. 4.

5. 6.

In Exercises 7–10, determine whether each value of x is asolution of the inequality.

Inequality Values

7. (a) (b)

(c) (d)

8. (a) (b)

(c) (d)

9. (a) (b)

(c) (d)

10. (a) (b)

(c) (d)

In Exercises 11– 20, solve the inequality and sketch thesolution on the real number line. Use a graphing utility toverify your solution graphically.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

Graphical Analysis In Exercises 21–24, use a graphingutility to approximate the solution.

21.

22.

23.

24.

In Exercises 25–28, use a graphing utility to graph theequation and graphically approximate the values of x thatsatisfy the specified inequalities. Then solve each inequalityalgebraically.

Equation Inequalities

25. (a) (b)

26. (a) (b)

27. (a) (b)

28. (a) (b) y ≥ 0y ≤ 5y �23x � 1

y ≥ 00 ≤ y ≤ 3y � �12 x � 2

y ≤ 0�1 ≤ y ≤ 3y � �3x � 8

y ≤ 0y ≥ 1y � 2x � 3

4�x � 3� ≤ 8 � x

3�x � 1� < x � 7

20 < 6x � 1

5 � 2x ≥ 1

0 ≤x � 3

2< 5

�4 <2x � 3

3< 4

0 ≤ 2 � 3�x � 1� < 20

�8 ≤ 1 � 3�x � 2� < 13

3 �27 x > x � 2

34x � 6 ≤ x � 7

2x � 7 < 3�x � 4�4�x � 1� < 2x � 3

6x > 15

�10x < 40

x � 9x � 14

x � �1x � 13�x � 10� ≥ 3

x � 5x � 1

x � 5x � 0�1 <3 � x

2≤ 1

x � 0x �43

x � �52x � �

12�5 < 2x � 1 ≤ 1

x �32x �

52

x � �3x � 35x � 12 > 0

�1 < x < 52�1 ≤ x ≤ 5

2

0 ≤ x ≤ 92�3 < x ≤ 4

x ≥ 5x < 3

x

65432

x

−2 −1 0 1 2 3 4 5 6−3

x

−2 −1 0 1 2 3 4 5 6−3

x

−2 −1 0 1 2 3 4 5 6−3

x

−1 0 1 2 3 4 5

x

4 5 6 7 8


Vocabulary Check

Fill in the blanks.

1. To solve a linear inequality in one variable, you can use the properties of inequalities, which are identical to those used to solve an equation, with the exception of multiplying or dividing each side by a _______ constant.

2. It is sometimes possible to write two inequalities as one inequality, called a _______ inequality.

3. The solutions to are those values of such that _______ .

4. The solutions to are those values of such that _______ or _______ .

5. The critical numbers of a rational expression are its _______ and its _______ .

x�x� ≥ a

x�x� ≤ a

333353_APPB4.qxp 1/22/07 8:54 AM Page A72


In Exercises 29 –36, solve the inequality and sketch thesolution on the real number line. Use a graphing utility toverify your solutions graphically.

29. 30.

31. 32.

33. 34.

35. 36.

In Exercises 37 and 38, use a graphing utility to graph theequation and graphically approximate the values of x thatsatisfy the specified inequalities. Then solve each inequalityalgebraically.


37. (a) (b)

38. (a) (b)

In Exercises 39–46, use absolute value notation to define theinterval (or pair of intervals) on the real number line.

39.

40.

41.

42.

43. All real numbers within 10 units of 7

44. All real numbers no more than 8 units from

45. All real numbers at least 5 units from 3

46. All real numbers more than 3 units from

In Exercises 47–52, determine the intervals on which thepolynomial is entirely negative and those on which it isentirely positive.

47. 48.

49. 50.

51. 52.

In Exercises 53–62, solve the inequality and graph thesolution on the real number line. Use a graphing utility toverify your solution graphically.

53. 54.

55. 56.

57. 58.

59. 60.

61. 62.

In Exercises 63 and 64, use the graph of the function to solvethe equation or inequality.

(a) (b) (c)

63. 64.



65. (a) (b)

66. (a) (b)

In Exercises 67–70, solve the inequality and graph thesolution on the real number line. Use a graphing utility toverify your solution graphically.

67. 68.

69. 70.



71. (a) (b)

72. (a) (b)

In Exercises 73–78, find the domain of x in the expression.

73. 74.

75. 76.

77. 78. 44 � x2x2 � 4

32x2 � 836 � x

46x � 15x � 5

y ≤ 0y ≥ 1y �5x

x 2 � 4

y ≥ 6y ≤ 0y �3x

x � 2

x � 12

x � 2� 3 ≥ 0

x � 6

x � 1� 2 < 0

1

x� 4 < 0

1

x� x > 0

y ≥ 36y ≤ 0y � x 3 � x 2 � 16x � 16

y ≥ 3y ≤ 0y � �x 2 � 2x � 3

−4−6 4 6

2

4

6

8

(−1, −3)

(3, 5)

y = f(x)

y = g(x)

x

y

−2−4 2 4−2

−4

2

x

y

(1, 2)

y = f(x)y = g(x)

f �x� > g�x�f �x� ~ g�x�f �x� � g�x�

2x3 � 3x2 < 11x � 62x3 � 5x2 > 6x � 9

4x2 � 12x � 9 ≤ 03x2 � 11x � 16 ≤ 0

x 4�x � 3� ≤ 0x3 � 4x ≥ 0

x 2 � 6x � 9 < 16x 2 � 4x � 4 ≥ 9

�x � 3�2≥ 1�x � 2�2 < 25

�x2 � 6x � 10x2 � 4x � 5

2x2 � x � 52x2 � 4x � 3

x2 � 3x � 4x2 � 4x � 5

�1

�5

x

4 5 6 7 8 9 10 11 12 13 14

x

3210−1−2−3

x

3210−1−2−3−4−5−6−7

x

−3 −2 −1 3210

y ≥ 1y ≤ 4y � �12x � 1�

y ≥ 4y ≤ 2y � �x � 3�

3�4 � 5x� ≤ 910�1 � 2x� < 5

�x � 3

2 � ≥ 5�x � 14� � 3 > 17

�x � 20� ≥ 4�x � 7� < 6

�x2� ≤ 1�5x� > 10

333353_APPB4.qxp 1/22/07 8:54 AM Page A73


79. Population The graph models the population P (inthousands) of Las Vegas, Nevada from 1990 to 2004, wheret is the year, with corresponding to 1990. Also shownis the line . Use the graphs of the model and thehorizontal line to write an equation or an inequality thatcould be solved to answer the question. Then answer thequestion. (Source: U.S. Census Bureau)

(a) In what year does the population of Las Vegas reachone million?

(b) Over what time period is the population of Las Vegasless than one million? greater than one million?

80. Population The graph models the population P (inthousands) of Pittsburgh, Pennsylvania from 1993 to 2004,where t is the year, with corresponding to 1993. Alsoshown is the line Use the graphs of the modeland the horizontal line to write an equation or an inequalitythat could be solved to answer the question. Then answerthe question. (Source: U.S. Census Bureau)

(a) In what year did the population of Pittsburgh equal 2.45 million?

(b) Over what time period is the population of Pittsburghless than 2.45 million? greater than 2.45 million?

81. Height of a Projectile A projectile is fired straightupward from ground level with an initial velocity of 160 feet per second.

(a) At what instant will it be back at ground level?

(b) When will the height exceed 384 feet?

82. Height of a Projectile A projectile is fired straightupward from ground level with an initial velocity of 128 feet per second.

(a) At what instant will it be back at ground level?

(b) When will the height be less than 128 feet?

83. Education The numbers D of doctorate degrees (inthousands) awarded to female students from 1990 to 2003in the United States can be approximated by the model

where t isthe year, with corresponding to 1990. (Source: U.S.National Center for Education Statistics)

(a) Use a graphing utility to graph the model.

(b) Use the zoom and trace features to find when thenumber of degrees was between 15 and 20 thousand.

(c) Algebraically verify your results from part (b).

(d) According to the model, will the number of degreesexceed 30 thousand? If so, when? If not, explain.

84. Data Analysis You want to determine whether there is arelationship between an athlete’s weight (in pounds) andthe athlete’s maximum bench-press weight (in pounds).Sample data from 12 athletes is shown below.

(a) Use a graphing utility to plot the data.

(b) A model for this data is Use a graphingutility to graph the equation in the same viewingwindow used in part (a).

(c) Use the graph to estimate the value of that predict amaximum bench-press weight of at least 200 pounds.

(d) Use the graph to write a statement about the accuracyof the model. If you think the graph indicates that anathlete’s weight is not a good indicator of the athlete’smaximum bench-press weight, list other factors thatmight influence an individual’s maximum bench-pressweight.

Leisure Time In Exercises 85–88, use the models belowwhich approximate the annual numbers of hours perperson spent reading daily newspapers N and playing videogames V for the years 2000 to 2005, where t is the year, with

corresponding to 2000. (Source: Veronis SuhlerStevenson)

Daily Newspapers:

Video Games:

85. Solve the inequality Explain what the solutionof the inequality represents.


87. Solve the equation Explain what the solutionof the equation represents.


V�t� > N�t�.

V�t� � N�t�.

N�t� ≤ 175.

V�t� ≥ 65.

V � 3.37t 1 57.9, 0 } t } 5

N � �2.51t 1 179.6, 0 } t } 5

t � 0

x

y � 1.3x � 36.

�160, 150��230, 250�,�190, 185�,�185, 195�,�170, 175�,�202, 190�,�240, 295�,

�196, 205�, �210, 255�,�150, 200�,�184, 185�,�165, 170�,

yx

t � 00 ≤ t ≤ 13,D � �0.0165t2 � 0.755t � 14.06,

Popu

latio

n(i

n th

ousa

nds)

Year (3 ↔ 1993)

t

y = P(t)

y = 2450

P

4 6 8 10 12

2300

2400

2500

2600

14

y � 2450.t � 3

Popu

latio

n(i

n th

ousa

nds)

Year (0 ↔ 1990)

t

y = P(t)

y = 1000

P

2 4 6 8 10 12 14

400800

120016002000

y � 1000t � 0

333353_APPB4.qxp 1/22/07 8:55 AM Page A74


Music In Exercises 89 –92, use the following information.Michael Kasha of Florida State University used physics andmathematics to design a new classical guitar. He used themodel for the frequency of the vibrations on a circular plate

where is the frequency (in vibrations per second),is the plate thickness (in millimeters), is the diameter of

the plate, is the elasticity of the plate material, and is thedensity of the plate material. For fixed values of and the graph of the equation is a line, as shown in the figure.

89. Estimate the frequency when the plate thickness is 2 millimeters.

90. Estimate the plate thickness when the frequency is 600vibrations per second.

91. Approximate the interval for the plate thickness when thefrequency is between 200 and 400 vibrations per second.

92. Approximate the interval for the frequency when the platethickness is less than 3 millimeters.

In Exercises 93 and 94, (a) write equations that representeach option, (b) use a graphing utility to graph the optionsin the same viewing window, (c) determine when eachoption is the better choice, and (d) explain which optionyou would choose.

93. Cellular Phones You are trying to decide between twodifferent cellular telephone contracts, option A and optionB. Option A has a monthly fee of $12 plus $0.15 perminute. Option B has no monthly fee but charges $0.20 perminute. All other monthly charges are identical.

94. Moving You are moving from your home to your dormroom, and the moving company has offered you twooptions. The charges for gasoline, insurance, and all otherincidental fees are equal.

Option A: $200 plus $18 per hour to move all of yourbelongings from your home to your dorm room.

Option B: $24 per hour to move all of your belongingsfrom your home to your dorm room.

Synthesis

True or False? In Exercises 95 and 96, determine whetherthe statement is true or false. Justify your answer.

95. If then and

96. The solution set of the inequality is theentire set of real numbers.

In Exercises 97 and 98, consider the polynomialand the real number line (see figure).

97. Identify the points on the line where the polynomial iszero.

98. In each of the three subintervals of the line, write the signof each factor and the sign of the product. For which

values does the polynomial possibly change signs?

99. Proof The arithmetic mean of a and b is given byOrder the statements of the proof to show that

if then

i.

ii.

iii.

iv.

100. Proof The geometric mean of a and b is given by Order the statements of the proof to show that if

then

i.

ii.

iii. a < ab < b

0 < a < b

a2 < ab < b2

a < ab < b.0 < a < b,

ab.

a < b

2a < a � b < 2b

2a < 2b

a <a � b

2< b

a < �a � b��2 < b.a < b,�a � b��2.

x-

a bx

�x � a��x � b�

32 x2 � 3x � 6 ≥ 0

�x ≥ �8.�10 ≥ �x�10 ≤ x ≤ 8,

Plate thickness (millimeters)

Freq

uenc

y(v

ibra

tions

per

seco

nd)

t

v

1 2 3 4

100

200

300

400

500

600

700

�,E,d,�E

dtv

v �2.6td2 E

�

333353_APPB4.qxp 1/22/07 8:55 AM Page A75


B.5 Representing Data Graphically

What you should learn� Use line plots to order and analyze data.

� Use histograms to represent frequency

distributions.

� Use bar graphs to represent and analyze

data.

� Use line graphs to represent and analyze

data.

Why you should learn itDouble bar graphs allow you to compare

visually two sets of data over time. For

example, in Exercises 9 and 10 on page A82,

you are asked to estimate the difference

in tuition between public and private

institutions of higher education.

Line PlotsStatistics is the branch of mathematics that studies techniques for collecting,organizing, and interpreting data. In this section, you will study several ways toorganize data. The first is a line plot, which uses a portion of a real number lineto order numbers. Line plots are especially useful for ordering small sets ofnumbers (about 50 or less) by hand.

Many statistical measures can be obtained from a line plot. Two suchmeasures are the frequency and range of the data. The frequency measures thenumber of times a value occurs in a data set. The range is the difference betweenthe greatest and smallest data values. For example, consider the data values

20, 21, 21, 25, 32.

The frequency of 21 in the data set is 2 because 21 occurs twice. The range is 12because the difference between the greatest and smallest data values is32 � 20 � 12.

Example 1 Constructing a Line Plot

Use a line plot to organize the following test scores. Which score occurs with thegreatest frequency? What is the range of scores?

93, 70, 76, 67, 86, 93, 82, 78, 83, 86, 64, 78, 76, 66, 8383, 96, 74, 69, 76, 64, 74, 79, 76, 88, 76, 81, 82, 74, 70

SolutionBegin by scanning the data to find the smallest and largest numbers. For the data,the smallest number is 64 and the largest is 96. Next, draw a portion of a realnumber line that includes the interval To create the line plot, start withthe first number, 93, and enter an above 93 on the number line. Continuerecording ’s for each number in the list until you obtain the line plot shown inFigure B.69. From the line plot, you can see that 76 occurs with the greatestfrequency. Because the range is the difference between the greatest and smallestdata values, the range of scores is

Figure B.69

Now try Exercise 1.

65 70 75 80 85 90 95 100

××

×× ×××

×××

×××××

××

× ×××

×××

××

× ××

×

Test scores

96 � 64 � 32.

�

�

�64, 96�.

333353_APPB5.qxp 1/22/07 8:55 AM Page A76

Appendix B.5 Representing Data Graphically A77

Histograms and Frequency DistributionsWhen you want to organize large sets of data, it is useful to group the data into intervals and plot the frequency of the data in each interval. A frequencydistribution can be used to construct a histogram. A histogram uses a portion ofa real number line as its horizontal axis. The bars of a histogram are not separatedby spaces.

Example 2 Constructing a Histogram

The table at the right shows the percent of the resident population of each state andthe District of Columbia that was at least 65 years old in 2004. Construct afrequency distribution and a histogram for the data. (Source: U.S. Census Bureau)

SolutionTo begin constructing a frequency distribution, you must first decide on thenumber of intervals. There are several ways to group the data. However, becausethe smallest number is 6.4 and the largest is 16.8, it seems that six intervals wouldbe appropriate. The first would be the interval the second would be and so on. By tallying the data into the six intervals, you obtain the frequencydistribution shown below. You can construct the histogram by drawing a verticalaxis to represent the number of states and a horizontal axis to represent thepercent of the population 65 and older. Then, for each interval, draw a vertical barwhose height is the total tally, as shown in Figure B.70.

Interval Tally

Figure B.70

Now try Exercise 5.

��16, 18�� 14, 16�

�� 12, 14�� 10, 12��8, 10��6, 8�

�8, 10�,�6, 8�,

AK 6.4AL 13.2AR 13.8AZ 12.7CA 10.7CO 9.8CT 13.5DC 12.1DE 13.1FL 16.8GA 9.6HI 13.6IA 14.7ID 11.4IL 12.0IN 12.4KS 13.0KY 12.5LA 11.7MA 13.3MD 11.4ME 14.4MI 12.3MN 12.1MO 13.3MS 12.2

MT 13.7NC 12.1ND 14.7NE 13.3NH 12.1NJ 12.9NM 12.1NV 11.2NY 13.0OH 13.3OK 13.2OR 12.8PA 15.3RI 13.9SC 12.4SD 14.2TN 12.5TX 9.9UT 8.7VA 11.4VT 13.0WA 11.3WI 13.0WV 15.3WY 12.1

333353_APPB5.qxp 1/22/07 8:55 AM Page A77


Bar GraphsA bar graph is similar to a histogram, except that the bars can be eitherhorizontal or vertical and the labels of the bars are not necessarily numbers.Another difference between a bar graph and a histogram is that the bars in a bargraph are usually separated by spaces.

Example 3 Constructing a Histogram

A company has 48 sales representatives who sold the following numbers of unitsduring the first quarter of 2008. Construct a frequency distribution for the data.

107 162 184 170 177 102 145 141

105 193 167 149 195 127 193 191

150 153 164 167 171 163 141 129

109 171 150 138 100 164 147 153

171 163 118 142 107 144 100 132

153 107 124 162 192 134 187 177

SolutionTo begin constructing a frequency distribution, you must first decide on thenumber of intervals. There are several ways to group the data. However, becausethe smallest number is 100 and the largest is 195, it seems that 10 intervals wouldbe appropriate. The first interval would be 100–109, the second would be110–119, and so on. By tallying the data into the 10 intervals, you obtain thedistribution shown at the right above. A histogram for the distribution is shown inFigure B.71.

Now try Exercise 6.

Units sold

Num

ber

of s

ales

repr

esen

tativ

es

100 200160120 180140

12345678

Unit Sales

Figure B.71

Mon

thly

nor

mal

prec

ipita

tion

(in

inch

es)

Month

1

2

3

4

5

6

J M M J S N

Monthly Precipitation

Figure B.72

Interval Tally

100–109110–119120–129130–139140–149150–159160–169170–179180–189190–199 ��

��

Example 4 Constructing a Bar Graph

The data below show the monthly normal precipitation (in inches) in Houston,Texas. Construct a bar graph for the data. What can you conclude? (Source:National Climatic Data Center)

January 3.7 February 3.0 March 3.4

April 3.6 May 5.2 June 5.4

July 3.2 August 3.8 September 4.3

October 4.5 November 4.2 December 3.7

SolutionTo create a bar graph, begin by drawing a vertical axis to represent the precipita-tion and a horizontal axis to represent the month. The bar graph is shown inFigure B.72. From the graph, you can see that Houston receives a fairly consis-tent amount of rain throughout the year—the driest month tends to be Februaryand the wettest month tends to be June.

Now try Exercise 7.

333353_APPB5.qxp 1/22/07 8:56 AM Page A78

Line GraphsA line graph is similar to a standard coordinate graph. Line graphs are usuallyused to show trends over periods of time.

Example 5 Constructing a Double Bar Graph

The table shows the percents of associate degrees awarded to males and femalesfor selected fields of study in the United States in 2003. Construct a double bargraph for the data. (Source: U.S. National Center for Education Statistics)

SolutionFor the data, a horizontal bar graph seems to be appropriate. This makes it easierto label and read the bars. Such a graph is shown in Figure B.73.

Figure B.73


Agriculture and Natural Resources

Biological Sciences/Life Sciences

Business and Management

Fiel

d of

stu

dy

Percent of associate degrees

Education

Engineering

Law and Legal Studies

Liberal/General Studies

Mathematics

Physical Sciences

Social Sciences

10 20 30 40 50 60 70 80 90 100

FemaleMale

Associate Degrees

Field of Study % Female % Male

Agriculture and Natural Resources 36.4 63.6

Biological Sciences/ Life Sciences 70.4 29.6

Business and Management 66.8 33.2

Education 80.5 19.5

Engineering 16.5 83.5

Law and Legal Studies 89.6 10.4

Liberal/General Sciences 63.1 36.9

Mathematics 36.5 63.5

Physical Sciences 44.7 55.3

Social Sciences 65.3 34.7


333353_APPB5.qxp 1/22/07 8:56 AM Page A79


Example 6 Constructing a Line Graph

The table at the right shows the number of immigrants (in thousands) entering theUnited States for each decade from 1901 to 2000. Construct a line graph for thedata. What can you conclude? (Source: U.S. Immigration and NaturalizationService)

SolutionBegin by drawing a vertical axis to represent the number of immigrants in thou-sands. Then label the horizontal axis with decades and plot the points shown inthe table. Finally, connect the points with line segments, as shown in Figure B.74.From the line graph, you can see that the number of immigrants hit a low pointduring the depression of the 1930s. Since then the number has steadily increased.

Figure B.74


You can use a graphing utility to create different typesof graphs, such as line graphs. For instance, the table at the right shows thenumbers N (in thousands) of women on active duty in the United States militaryfor selected years. To use a graphing utility to create a line graph of the data,first enter the data into the graphing utility’s list editor, as shown in FigureB.75. Then use the statistical plotting feature to set up the line graph, as shownin Figure B.76. Finally, display the line graph use a viewing window in which

and , as shown in Figure B.77. (Source: U.S.Department of Defense)


0 ≤ y ≤ 250�1970 ≤ x ≤ 2010�

TECHNOLOGY T I P

1970 2010

250

0

Year Number

1975 971980 1711985 2121990 2271995 1962000 2032005 203

Decade Number

1901–1910 87951911–1920 57361921–1930 41071931–1940 5281941–1950 10351951–1960 25151961–1970 33221971–1980 44931981–1990 73381991–2000 9095

333353_APPB5.qxp 1/22/07 8:56 AM Page A80


1. Consumer Awareness The line plot shows a sample ofprices of unleaded regular gasoline in 25 different cities.

(a) What price occurred with the greatest frequency?

(b) What is the range of prices?

2. Agriculture The line plot shows the weights (to the nearesthundred pounds) of 30 head of cattle sold by a rancher.

(a) What weight occurred with the greatest frequency?

(b) What is the range of weights?

Quiz and Exam Scores In Exercises 3 and 4, use the following scores from an algebra class of 30 students. Thescores are for one 25-point quiz and one 100-point exam.

Quiz 20, 15, 14, 20, 16, 19, 10, 21, 24, 15, 15, 14, 15, 21, 19,15, 20, 18, 18, 22, 18, 16, 18, 19, 21, 19, 16, 20, 14, 12

Exam 77, 100, 77, 70, 83, 89, 87, 85, 81, 84, 81, 78, 89, 78,88, 85, 90, 92, 75, 81, 85, 100, 98, 81, 78, 75, 85, 89, 82, 75

3. Construct a line plot for the quiz. Which score(s) occurredwith the greatest frequency?

4. Construct a line plot for the exam. Which score(s) occurredwith the greatest frequency?

5. Agriculture The list shows the numbers of farms (in thou-sands) in the 50 states in 2004. Use a frequency distributionand a histogram to organize the data. (Source: U.S.Department of Agriculture)

AK 1 AL 44 AR 48 AZ 10CA 77 CO 31 CT 4 DE 2FL 43 GA 49 HI 6 IA 90ID 25 IL 73 IN 59 KS 65KY 85 LA 27 MA 6 MD 12ME 7 MI 53 MN 80 MO 106MS 42 MT 28 NC 52 ND 30NE 48 NH 3 NJ 10 NM 18NV 3 NY 36 OH 77 OK 84OR 40 PA 58 RI 1 SC 24SD 32 TN 85 TX 229 UT 15VA 48 VT 6 WA 35 WI 77WV 21 WY 9

6. Schools The list shows the numbers of public high schoolgraduates (in thousands) in the 50 states and the District ofColumbia in 2004. Use a frequency distribution and ahistogram to organize the data. (Source: U.S. NationalCenter for Education Statistics)

AK 7.1 AL 37.6 AR 26.9 AZ 57.0CA 342.6 CO 42.9 CT 34.4 DC 3.2DE 6.8 FL 129.0 GA 69.7 HI 10.3IA 33.8 ID 15.5 IL 121.3 IN 57.6KS 30.0 KY 36.2 LA 36.2 MA 57.9MD 53.0 ME 13.4 MI 106.3 MN 59.8MO 57.0 MS 23.6 MT 10.5 NC 71.4ND 7.8 NE 20.0 NH 13.3 NJ 88.3NM 18.1 NV 16.2 NY 150.9 OH 116.3OK 36.7 OR 32.5 PA 121.6 RI 9.3SC 32.1 SD 9.1 TN 43.6 TX 236.7UT 29.9 VA 71.7 VT 7.0 WA 60.4WI 62.3 WV 17.1 WY 5.7

××

×××

××××

×××××××××

××××

××××××

××

600 800 1000 1200 1400

2.449 2.469 2.489 2.509 2.529 2.549 2.569 2.589 2.609 2.629 2.649

× × × ×××

× ××

××××××

××

××

× ××××

×


Vocabulary Check

Fill in the blanks.

1. _______ is the branch of mathematics that studies techniques for collecting, organizing, and interpreting data.

2. _______ are useful for ordering small sets of numbers by hand.

3. A _______ uses a portion of a real number line as its horizontal axis, and the bars are not separated by spaces.

4. You use a _______ to construct a histogram.

5. The bars in a _______ can be either vertical or horizontal.

6. _______ show trends over periods of time.

333353_APPB5.qxp 1/22/07 8:56 AM Page A81


7. Business The table shows the numbers of Wal-Martstores from 1995 to 2006. Construct a bar graph for thedata. Write a brief statement regarding the number of Wal-Mart stores over time. (Source: Value Line)

8. Business The table shows the revenues (in billions ofdollars) for Costco Wholesale from 1995 to 2006.Construct a bar graph for the data. Write a brief statementregarding the revenue of Costco Wholesale stores overtime. (Source: Value Line)

Tuition In Exercises 9 and 10, the double bar graph showsthe mean tuitions (in dollars) charged by public and privateinstitutions of higher education in the United States from1999 to 2004. (Source: U.S. National Center for EducationStatistics)

9. Approximate the difference in tuition charges for publicand private schools for each year.

10. Approximate the increase or decrease in tuition charges foreach type of institution from year to year.

11. College Enrollment The table shows the total collegeenrollments (in thousands) for women and men in theUnited States from 1997 to 2003. Construct a double bargraph for the data. (Source: U.S. National Center forEducation Statistics)

12. Population The table shows the populations (in millions)in the coastal regions of the United States in 1970 and2003. Construct a double bar graph for the data. (Source:U.S. Census Bureau)

6,000

2,000

4,000

8,000

1999 2000 2001 2002 2003 2004

10,000

12,000

14,000

16,000

18,000 PublicPrivate

Tui

tion

(in

dolla

rs)

Year Number of stores

1995 2943

1996 3054

1997 3406

1998 3599

1999 3985

2000 4189

2001 4414

2002 4688

2003 4906

2004 5289

2005 5650

2006 6050

YearRevenue

(in billions of dollars)

1995 18.247

1996 19.566

1997 21.874

1998 24.270

1999 27.456

2000 32.164

2001 34.797

2002 38.762

2003 42.546

2004 48.107

2005 52.935

2006 58.600

YearWomen

(in thousands)Men

(in thousands)

1997 8106.3 6396.0

1998 8137.7 6369.3

1999 8300.6 6490.6

2000 8590.5 6721.8

2001 8967.2 6960.8

2002 9410.0 7202.0

2003 9652.0 7259.0

Region1970

population(in millions)

2003population

(in millions)

Atlantic 52.1 67.1

Gulf of Mexico 10.0 18.9

Great Lakes 26.0 27.5

Pacific 22.8 39.4

333353_APPB5.qxp 1/22/07 8:56 AM Page A82

Advertising In Exercises 13 and 14, use the line graph,which shows the costs of a 30-second television spot (inthousands of dollars) during the Super Bowl from 1995 to2005. (Source: The Associated Press)

13. Approximate the percent increase in the cost of a 30-second spot from Super Bowl XXX in 1996 to SuperBowl XXXIX in 2005.

14. Estimate the increase or decrease in the cost of a 30-second spot from (a) Super Bowl XXIX in 1995 toSuper Bowl XXXIII in 1999, and (b) Super Bowl XXXIVin 2000 to Super Bowl XXXIX in 2005.

Retail Price In Exercises 15 and 16, use the line graph,which shows the average retail price (in dollars) of onepound of 100% ground beef in the United States for eachmonth in 2004. (Source: U.S. Bureau of Labor Statistics)

15. What is the highest price of one pound of 100% groundbeef shown in the graph? When did this price occur?

16. What was the difference between the highest price and thelowest price of one pound of 100% ground beef in 2004?

17. Labor The table shows the total numbers of women inthe work force (in thousands) in the United States from1995 to 2004. Construct a line graph for the data. Write abrief statement describing what the graph reveals.(Source: U.S. Bureau of Labor Statistics)

18. SAT Scores The table shows the average ScholasticAptitude Test (SAT) Math Exam scores for college-boundseniors in the United States for selected years from 1970 to2005. Construct a line graph for the data. Write a briefstatement describing what the graph reveals. (Source:The College Entrance Examination Board)

19. Hourly Earnings The table on page A84 shows theaverage hourly earnings (in dollars) of production workersin the United States from 1994 to 2005. Use a graphingutility to construct a line graph for the data. (Source: U.S.Bureau of Labor Statistics)

Ret

ail p

rice

(in

dol

lars

)

MonthJan. Mar. May July Sept. Nov.

2.30

2.40

2.50

2.60

2.70

2.80

Year

1000

1200

1400

1600

1800

2000

2200

2400

Cos

t of

a 30

-sec

ond

TV

spo

t(i

n th

ousa

nds

of d

olla

rs)

1995 1997 1999 2001 2003 2005

Year SAT scores

1970 512

1975 498

1980 492

1985 500

1990 501

1995 506

2000 514

2005 520

YearWomen in the work force

(in thousands)

1995 60,944

1996 61,857

1997 63,036

1998 63,714

1999 64,855

2000 66,303

2001 66,848

2002 67,363

2003 68,272

2004 68,421


333353_APPB5.qxp 1/22/07 8:56 AM Page A83


20. Internet Access The list shows the percent of householdsin each of the 50 states and the District of Columbia withInternet access in 2003. Use a graphing utility to organizethe data in the graph of your choice. Explain your choice ofgraph. (Source: U.S. Department of Commerce)

AK 67.6 AL 45.7 AR 42.4 AZ 55.2CA 59.6 CO 63.0 CT 62.9 DC 53.2DE 56.8 FL 55.6 GA 53.5 HI 55.0IA 57.1 ID 56.4 IL 51.1 IN 51.0KS 54.3 KY 49.6 LA 44.1 MA 58.1MD 59.2 ME 57.9 MI 52.0 MN 61.6MO 53.0 MS 38.9 MT 50.4 NC 51.1ND 53.2 NE 55.4 NH 65.2 NJ 60.5NM 44.5 NV 55.2 NY 53.3 OH 52.5OK 48.4 OR 61.0 PA 54.7 RI 55.7SC 45.6 SD 53.6 TN 48.9 TX 51.8UT 62.6 VA 60.3 VT 58.1 WA 62.3WI 57.4 WV 47.6 WY 57.7

Cellular Phones In Exercises 21 and 22, use the table,which shows the average monthly cellular telephone bills (indollars) in the United States from 1999 to 2004. (Source:Telecommunications & Internet Association)

21. Organize the data in an appropriate display. Explain yourchoice of graph.

22. The average monthly bills in 1990 and 1995 were $80.90and $51.00, respectively. How would you explain thetrend(s) in the data?

23. High School Athletes The table shows the numbers ofparticipants (in thousands) in high school athletic programsin the United States from 1995 to 2004. Organize the datain an appropriate display. Explain your choice of graph.(Source: National Federation of State High SchoolAssociations)

Synthesis

24. Writing Describe the differences between a bar graphand a histogram.

25. Think About It How can you decide which type of graphto use when you are organizing data?

26. Graphical Interpretation The graphs shown below rep-resent the same data points. Which of the two graphs ismisleading, and why? Discuss other ways in which graphscan be misleading. Try to find another example of a mis-leading graph in a newspaper or magazine. Why is it mis-leading? Why would it be beneficial for someone to use amisleading graph?

32.0

32.4

32.8

33.2

33.6

34.0

34.4

NSJMMJ

Month

Com

pany

pro

fits

0

10

20

30

40

50

MonthJ M M J S N

Com

pany

pro

fitsYear

Average monthly bill (in dollars)

1999 41.24

2000 45.27

2001 47.37

2002 48.40

2003 49.91

2004 50.64

YearFemale athletes (in thousands)

Male athletes (in thousands)

1995 2240 3536

1996 2368 3634

1997 2474 3706

1998 2570 3763

1999 2653 3832

2000 2676 3862

2001 2784 3921

2002 2807 3961

2003 2856 3989

2004 2865 4038

YearHourly earnings

(in dollars)

1994 11.19

1995 11.47

1996 11.84

1997 12.27

1998 12.77

1999 13.25

2000 13.73

2001 14.27

2002 14.73

2003 15.19

2004 15.48

2005 15.90

Table for 19

333353_APPB5.qxp 1/22/07 8:56 AM Page A84

appendix b.1 the cartesian plane a25 333353 appb1 pg a25

Documents