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Frank Ma © 2011 More on Slopes

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Page 1: 37 more on slopes-x

Frank Ma © 2011

More on Slopes

Page 2: 37 more on slopes-x

Definition of Slope More on Slopes

Page 3: 37 more on slopes-x

Definition of Slope Let (x1, y1) and (x2, y2) be two points on a line,

(x1, y1)

(x2, y2)

More on Slopes

Page 4: 37 more on slopes-x

Definition of Slope Let (x1, y1) and (x2, y2) be two points on a line, then the slope m of the line is

ΔyΔxm =

(x1, y1)

(x2, y2)

More on Slopes

Page 5: 37 more on slopes-x

Definition of Slope Let (x1, y1) and (x2, y2) be two points on a line, then the slope m of the line is

ΔyΔx

y2 – y1

x2 – x1m = =

(x1, y1)

(x2, y2)

More on Slopes

Page 6: 37 more on slopes-x

Definition of Slope Let (x1, y1) and (x2, y2) be two points on a line, then the slope m of the line is

ΔyΔx

y2 – y1

x2 – x1m = =

Geometry of Slope

(x1, y1)

(x2, y2)

More on Slopes

Page 7: 37 more on slopes-x

Definition of Slope Let (x1, y1) and (x2, y2) be two points on a line, then the slope m of the line is

ΔyΔx

y2 – y1

x2 – x1m = =

(x1, y1)

(x2, y2)

Δy=y2–y1=rise

Geometry of Slope Δy = y2 – y1 = the difference in the heights of the points.

More on Slopes

Page 8: 37 more on slopes-x

Definition of Slope Let (x1, y1) and (x2, y2) be two points on a line, then the slope m of the line is

ΔyΔx

y2 – y1

x2 – x1m = =

(x1, y1)

(x2, y2)

Δy=y2–y1=rise

Δx=x2–x1=run

Geometry of Slope Δy = y2 – y1 = the difference in the heights of the points.Δx = x2 – x1 = the difference in the runs of the points.

More on Slopes

Page 9: 37 more on slopes-x

Definition of Slope Let (x1, y1) and (x2, y2) be two points on a line, then the slope m of the line is

ΔyΔx

y2 – y1

x2 – x1m = =

(x1, y1)

(x2, y2)

Δy=y2–y1=rise

Δx=x2–x1=run

Geometry of Slope Δy = y2 – y1 = the difference in the heights of the points.Δx = x2 – x1 = the difference in the runs of the points.

ΔyΔx= Therefore m is the ratio of the “rise” to the

“run”.

More on Slopes

Page 10: 37 more on slopes-x

Definition of Slope Let (x1, y1) and (x2, y2) be two points on a line, then the slope m of the line is

ΔyΔx

y2 – y1

x2 – x1m = =

riserun=

(x1, y1)

(x2, y2)

Δy=y2–y1=rise

Δx=x2–x1=run

Geometry of Slope Δy = y2 – y1 = the difference in the heights of the points.Δx = x2 – x1 = the difference in the runs of the points.

ΔyΔx= Therefore m is the ratio of the “rise” to the

“run”. m = Δy

Δxy2 – y1

x2 – x1=

More on Slopes

Page 11: 37 more on slopes-x

Definition of Slope Let (x1, y1) and (x2, y2) be two points on a line, then the slope m of the line is

ΔyΔx

y2 – y1

x2 – x1m = =

riserun=

(x1, y1)

(x2, y2)

Δy=y2–y1=rise

Δx=x2–x1=run

Geometry of Slope Δy = y2 – y1 = the difference in the heights of the points.Δx = x2 – x1 = the difference in the runs of the points.

ΔyΔx= Therefore m is the ratio of the “rise” to the

“run”. m = Δy

Δxy2 – y1

x2 – x1=

easy to memorize

More on Slopes

Page 12: 37 more on slopes-x

Definition of Slope Let (x1, y1) and (x2, y2) be two points on a line, then the slope m of the line is

ΔyΔx

y2 – y1

x2 – x1m = =

riserun=

(x1, y1)

(x2, y2)

Δy=y2–y1=rise

Δx=x2–x1=run

Geometry of Slope Δy = y2 – y1 = the difference in the heights of the points.Δx = x2 – x1 = the difference in the runs of the points.

ΔyΔx= Therefore m is the ratio of the “rise” to the

“run”. m = Δy

Δxy2 – y1

x2 – x1=

easy to memorize

the exact formula

More on Slopes

Page 13: 37 more on slopes-x

Definition of Slope Let (x1, y1) and (x2, y2) be two points on a line, then the slope m of the line is

ΔyΔx

y2 – y1

x2 – x1m = =

riserun=

(x1, y1)

(x2, y2)

Δy=y2–y1=rise

Δx=x2–x1=run

Geometry of Slope Δy = y2 – y1 = the difference in the heights of the points.Δx = x2 – x1 = the difference in the runs of the points.

ΔyΔx= Therefore m is the ratio of the “rise” to the

“run”. m = Δy

Δxy2 – y1

x2 – x1=

easy to memorize

the exact formula

geometric meaning

More on Slopes

Page 14: 37 more on slopes-x

Example A. Find the slope of each of the following lines. More on Slopes

Page 15: 37 more on slopes-x

Example A. Find the slope of each of the following lines.

Two points are(–3, 1), (4, 1).

More on Slopes

Page 16: 37 more on slopes-x

Example A. Find the slope of each of the following lines.

Two points are(–3, 1), (4, 1).Δy = 1 – (1) = 0

More on Slopes

Page 17: 37 more on slopes-x

Example A. Find the slope of each of the following lines.

Two points are(–3, 1), (4, 1).Δy = 1 – (1) = 0Δx = 4 – (–3) = 7

More on Slopes

Page 18: 37 more on slopes-x

Example A. Find the slope of each of the following lines.

Two points are(–3, 1), (4, 1).Δy = 1 – (1) = 0Δx = 4 – (–3) = 7

More on Slopes

m = ΔyΔx = 0

7 = 0

Page 19: 37 more on slopes-x

Example A. Find the slope of each of the following lines.

Two points are(–3, 1), (4, 1).Δy = 1 – (1) = 0Δx = 4 – (–3) = 7

More on Slopes

m = ΔyΔx = 0

7Horizontal line Slope = 0

= 0

Page 20: 37 more on slopes-x

Example A. Find the slope of each of the following lines.

Two points are(–2, –4), (2, 3).

Two points are(–3, 1), (4, 1).Δy = 1 – (1) = 0Δx = 4 – (–3) = 7

More on Slopes

m = ΔyΔx = 0

7Horizontal line Slope = 0

= 0

Page 21: 37 more on slopes-x

Example A. Find the slope of each of the following lines.

Two points are(–2, –4), (2, 3).Δy = 3 – (–4) = 7

Two points are(–3, 1), (4, 1).Δy = 1 – (1) = 0Δx = 4 – (–3) = 7

More on Slopes

m = ΔyΔx = 0

7Horizontal line Slope = 0

= 0

Page 22: 37 more on slopes-x

Example A. Find the slope of each of the following lines.

Two points are(–2, –4), (2, 3).Δy = 3 – (–4) = 7Δx = 2 – (–2) = 4

Two points are(–3, 1), (4, 1).Δy = 1 – (1) = 0Δx = 4 – (–3) = 7

More on Slopes

m = ΔyΔx = 0

7Horizontal line Slope = 0

= 0

Page 23: 37 more on slopes-x

Example A. Find the slope of each of the following lines.

Two points are(–2, –4), (2, 3).Δy = 3 – (–4) = 7Δx = 2 – (–2) = 4

m =

Two points are(–3, 1), (4, 1).Δy = 1 – (1) = 0Δx = 4 – (–3) = 7

More on Slopes

ΔyΔx = 7

4m = ΔyΔx = 0

7Horizontal line Slope = 0

= 0

Page 24: 37 more on slopes-x

Example A. Find the slope of each of the following lines.

Two points are(–2, –4), (2, 3).Δy = 3 – (–4) = 7Δx = 2 – (–2) = 4

m =

Two points are(–3, 1), (4, 1).Δy = 1 – (1) = 0Δx = 4 – (–3) = 7

More on Slopes

ΔyΔx = 7

4m = ΔyΔx = 0

7Horizontal line Slope = 0

Tilted line Slope = 0

= 0

Page 25: 37 more on slopes-x

Example A. Find the slope of each of the following lines.

Two points are(–2, –4), (2, 3).Δy = 3 – (–4) = 7Δx = 2 – (–2) = 4

m =

Two points are(–3, 1), (4, 1).Δy = 1 – (1) = 0Δx = 4 – (–3) = 7

Two points are(–1, 3), (6, 3).

More on Slopes

ΔyΔx = 7

4m = ΔyΔx = 0

7Horizontal line Slope = 0

Tilted line Slope = 0

= 0

Page 26: 37 more on slopes-x

Example A. Find the slope of each of the following lines.

Two points are(–2, –4), (2, 3).Δy = 3 – (–4) = 7Δx = 2 – (–2) = 4

m =

Two points are(–3, 1), (4, 1).Δy = 1 – (1) = 0Δx = 4 – (–3) = 7

Two points are(–1, 3), (6, 3).Δy = 3 – 3 = 0

More on Slopes

ΔyΔx = 7

4m = ΔyΔx = 0

7Horizontal line Slope = 0

Tilted line Slope = 0

= 0

Page 27: 37 more on slopes-x

Example A. Find the slope of each of the following lines.

Two points are(–2, –4), (2, 3).Δy = 3 – (–4) = 7Δx = 2 – (–2) = 4

m =

Two points are(–3, 1), (4, 1).Δy = 1 – (1) = 0Δx = 4 – (–3) = 7

Two points are(–1, 3), (6, 3).Δy = 3 – 3 = 0Δx = 6 – (–1) = 7

More on Slopes

ΔyΔx = 7

4m = ΔyΔx = 0

7Horizontal line Slope = 0

Tilted line Slope = 0

= 0

Page 28: 37 more on slopes-x

Example A. Find the slope of each of the following lines.

Two points are(–2, –4), (2, 3).Δy = 3 – (–4) = 7Δx = 2 – (–2) = 4

m =

Two points are(–3, 1), (4, 1).Δy = 1 – (1) = 0Δx = 4 – (–3) = 7

Two points are(–1, 3), (6, 3).Δy = 3 – 3 = 0Δx = 6 – (–1) = 7

More on Slopes

ΔyΔx = 7

4m = ΔyΔx = 0

7m = Δy

Δx = 70

Horizontal line Slope = 0

Tilted line Slope = 0

= 0 (UDF)

Page 29: 37 more on slopes-x

Example A. Find the slope of each of the following lines.

Two points are(–2, –4), (2, 3).Δy = 3 – (–4) = 7Δx = 2 – (–2) = 4

m =

Two points are(–3, 1), (4, 1).Δy = 1 – (1) = 0Δx = 4 – (–3) = 7

Two points are(–1, 3), (6, 3).Δy = 3 – 3 = 0Δx = 6 – (–1) = 7

More on Slopes

ΔyΔx = 7

4m = ΔyΔx = 0

7m = Δy

Δx = 70

Horizontal line Slope = 0

Vertical line Slope is UDF

Tilted line Slope = 0

= 0 (UDF)

Page 30: 37 more on slopes-x

Lines that go through the quadrants I and III have positive slopes.

More on Slopes

Page 31: 37 more on slopes-x

Lines that go through the quadrants I and III have positive slopes.

More on Slopes

III

III IV

Page 32: 37 more on slopes-x

Lines that go through the quadrants I and III have positive slopes.

Lines that go through the quadrants II and IV have negative slopes.

More on Slopes

III

III IV

Page 33: 37 more on slopes-x

Lines that go through the quadrants I and III have positive slopes.

Lines that go through the quadrants II and IV have negative slopes.

More on Slopes

III

III IV

III

III IV

Page 34: 37 more on slopes-x

Lines that go through the quadrants I and III have positive slopes.

Lines that go through the quadrants II and IV have negative slopes.

More on Slopes

The formula for slopes requires geometric information,i.e. the positions of two points on the line.

III

III IV

III

III IV

Page 35: 37 more on slopes-x

Lines that go through the quadrants I and III have positive slopes.

Lines that go through the quadrants II and IV have negative slopes.

More on Slopes

The formula for slopes requires geometric information,i.e. the positions of two points on the line. However, if a line is given by its equation instead, we may determine the slope from the equation directly.

III

III IV

III

III IV

Page 36: 37 more on slopes-x

Given a linear equation in x and y, solve for the variable y if possible, we get y = mx + b

More on Slopes

Page 37: 37 more on slopes-x

Given a linear equation in x and y, solve for the variable y if possible, we get y = mx + bthe number m is the slope and b is the y-intercept.

More on Slopes

Page 38: 37 more on slopes-x

Given a linear equation in x and y, solve for the variable y if possible, we get y = mx + bthe number m is the slope and b is the y-intercept. This is called the slope intercept form and this can be doneonly if the y-term is present.

More on Slopes

Page 39: 37 more on slopes-x

Given a linear equation in x and y, solve for the variable y if possible, we get y = mx + bthe number m is the slope and b is the y-intercept. This is called the slope intercept form and this can be doneonly if the y-term is present.

More on Slopes

a. 3x = –2y + 6

Example B. Write the equations into the slope intercept form, list the slopes, the y-intercepts and draw the lines.

Page 40: 37 more on slopes-x

Given a linear equation in x and y, solve for the variable y if possible, we get y = mx + bthe number m is the slope and b is the y-intercept. This is called the slope intercept form and this can be doneonly if the y-term is present.

More on Slopes

a. 3x = –2y + 6 solve for y

Example B. Write the equations into the slope intercept form, list the slopes, the y-intercepts and draw the lines.

Page 41: 37 more on slopes-x

Given a linear equation in x and y, solve for the variable y if possible, we get y = mx + bthe number m is the slope and b is the y-intercept. This is called the slope intercept form and this can be doneonly if the y-term is present.

More on Slopes

a. 3x = –2y + 6 solve for y 2y = –3x + 6

Example B. Write the equations into the slope intercept form, list the slopes, the y-intercepts and draw the lines.

Page 42: 37 more on slopes-x

Given a linear equation in x and y, solve for the variable y if possible, we get y = mx + bthe number m is the slope and b is the y-intercept. This is called the slope intercept form and this can be doneonly if the y-term is present.

More on Slopes

a. 3x = –2y + 6 solve for y 2y = –3x + 6

y = 2–3 x + 3

Example B. Write the equations into the slope intercept form, list the slopes, the y-intercepts and draw the lines.

Page 43: 37 more on slopes-x

Given a linear equation in x and y, solve for the variable y if possible, we get y = mx + bthe number m is the slope and b is the y-intercept. This is called the slope intercept form and this can be doneonly if the y-term is present.

More on Slopes

a. 3x = –2y + 6 solve for y 2y = –3x + 6

y = 2–3 x + 3

Hence the slope m is –3/2

Example B. Write the equations into the slope intercept form, list the slopes, the y-intercepts and draw the lines.

Page 44: 37 more on slopes-x

Given a linear equation in x and y, solve for the variable y if possible, we get y = mx + bthe number m is the slope and b is the y-intercept. This is called the slope intercept form and this can be doneonly if the y-term is present.

More on Slopes

a. 3x = –2y + 6 solve for y 2y = –3x + 6

y = 2–3 x + 3

Hence the slope m is –3/2 and the y-intercept is (0, 3).

Example B. Write the equations into the slope intercept form, list the slopes, the y-intercepts and draw the lines.

Page 45: 37 more on slopes-x

Given a linear equation in x and y, solve for the variable y if possible, we get y = mx + bthe number m is the slope and b is the y-intercept. This is called the slope intercept form and this can be doneonly if the y-term is present.

More on Slopes

Example B. Write the equations into the slope intercept form, list the slopes, the y-intercepts and draw the lines.a. 3x = –2y + 6 solve for y 2y = –3x + 6

y = 2–3 x + 3

Hence the slope m is –3/2 and the y-intercept is (0, 3).Set y = 0, we get the x-intercept (2, 0).

Page 46: 37 more on slopes-x

Given a linear equation in x and y, solve for the variable y if possible, we get y = mx + bthe number m is the slope and b is the y-intercept. This is called the slope intercept form and this can be doneonly if the y-term is present.

More on Slopes

a. 3x = –2y + 6 solve for y 2y = –3x + 6

y = 2–3 x + 3

Hence the slope m is –3/2 and the y-intercept is (0, 3).Set y = 0, we get the x-intercept (2, 0). Use these points to draw the line.

Example B. Write the equations into the slope intercept form, list the slopes, the y-intercepts and draw the lines.

Page 47: 37 more on slopes-x

Given a linear equation in x and y, solve for the variable y if possible, we get y = mx + bthe number m is the slope and b is the y-intercept. This is called the slope intercept form and this can be doneonly if the y-term is present.

More on Slopes

a. 3x = –2y + 6 solve for y 2y = –3x + 6

y = 2–3 x + 3

Hence the slope m is –3/2 and the y-intercept is (0, 3).Set y = 0, we get the x-intercept (2, 0). Use these points to draw the line.

Example B. Write the equations into the slope intercept form, list the slopes, the y-intercepts and draw the lines.

Page 48: 37 more on slopes-x

b. 0 = –2y + 6More on Slopes

Page 49: 37 more on slopes-x

b. 0 = –2y + 6 solve for yMore on Slopes

Page 50: 37 more on slopes-x

b. 0 = –2y + 6 solve for y 2y = 6 y = 3

More on Slopes

Page 51: 37 more on slopes-x

b. 0 = –2y + 6 solve for y 2y = 6 y = 3 y = 0x + 3

More on Slopes

Page 52: 37 more on slopes-x

b. 0 = –2y + 6 solve for y 2y = 6 y = 3 y = 0x + 3

Hence the slope m is 0.

More on Slopes

Page 53: 37 more on slopes-x

b. 0 = –2y + 6 solve for y 2y = 6 y = 3 y = 0x + 3

Hence the slope m is 0. The y-intercept is (0, 3).

More on Slopes

Page 54: 37 more on slopes-x

b. 0 = –2y + 6 solve for y 2y = 6 y = 3 y = 0x + 3

Hence the slope m is 0. The y-intercept is (0, 3). There is no x-intercept.

More on Slopes

Page 55: 37 more on slopes-x

b. 0 = –2y + 6 solve for y 2y = 6 y = 3 y = 0x + 3

Hence the slope m is 0. The y-intercept is (0, 3). There is no x-intercept.

More on Slopes

Page 56: 37 more on slopes-x

b. 0 = –2y + 6 solve for y 2y = 6 y = 3 y = 0x + 3

Hence the slope m is 0. The y-intercept is (0, 3). There is no x-intercept.

c. 3x = 6

More on Slopes

Page 57: 37 more on slopes-x

b. 0 = –2y + 6 solve for y 2y = 6 y = 3 y = 0x + 3

Hence the slope m is 0. The y-intercept is (0, 3). There is no x-intercept.

c. 3x = 6

More on Slopes

The variable y can’t be isolated because there is no y.

Page 58: 37 more on slopes-x

b. 0 = –2y + 6 solve for y 2y = 6 y = 3 y = 0x + 3

Hence the slope m is 0. The y-intercept is (0, 3). There is no x-intercept.

c. 3x = 6

More on Slopes

The variable y can’t be isolated because there is no y.Hence the slope is undefinedand this is a vertical line.

Page 59: 37 more on slopes-x

b. 0 = –2y + 6 solve for y 2y = 6 y = 3 y = 0x + 3

Hence the slope m is 0. The y-intercept is (0, 3). There is no x-intercept.

c. 3x = 6

More on Slopes

The variable y can’t be isolated because there is no y.Hence the slope is undefinedand this is a vertical line.Solve for x 3x = 6 x = 2.

Page 60: 37 more on slopes-x

b. 0 = –2y + 6 solve for y 2y = 6 y = 3 y = 0x + 3

Hence the slope m is 0. The y-intercept is (0, 3). There is no x-intercept.

c. 3x = 6

More on Slopes

The variable y can’t be isolated because there is no y.Hence the slope is undefinedand this is a vertical line.Solve for x 3x = 6 x = 2.This is the vertical line x = 2.

Page 61: 37 more on slopes-x

b. 0 = –2y + 6 solve for y 2y = 6 y = 3 y = 0x + 3

Hence the slope m is 0. The y-intercept is (0, 3). There is no x-intercept.

c. 3x = 6

More on Slopes

The variable y can’t be isolated because there is no y.Hence the slope is undefinedand this is a vertical line.Solve for x 3x = 6 x = 2.This is the vertical line x = 2.

Page 62: 37 more on slopes-x

Two Facts About SlopesI. Parallel lines have the same slope.

More on Slopes

Page 63: 37 more on slopes-x

Two Facts About SlopesI. Parallel lines have the same slope.II. Slopes of perpendicular lines are the negative reciprocal of each other.

More on Slopes

Page 64: 37 more on slopes-x

Two Facts About SlopesI. Parallel lines have the same slope.II. Slopes of perpendicular lines are the negative reciprocal of each other.Example C. a. The line L is parallel to 4x – 2y = 5, what is the slope of L?

More on Slopes

Page 65: 37 more on slopes-x

Two Facts About SlopesI. Parallel lines have the same slope.II. Slopes of perpendicular lines are the negative reciprocal of each other.Example C. a. The line L is parallel to 4x – 2y = 5, what is the slope of L? Solve for y for 4x – 2y = 5

More on Slopes

Page 66: 37 more on slopes-x

Two Facts About SlopesI. Parallel lines have the same slope.II. Slopes of perpendicular lines are the negative reciprocal of each other.Example C. a. The line L is parallel to 4x – 2y = 5, what is the slope of L? Solve for y for 4x – 2y = 5 4x – 5 = 2y

More on Slopes

Page 67: 37 more on slopes-x

Two Facts About SlopesI. Parallel lines have the same slope.II. Slopes of perpendicular lines are the negative reciprocal of each other.Example C. a. The line L is parallel to 4x – 2y = 5, what is the slope of L? Solve for y for 4x – 2y = 5 4x – 5 = 2y 2x – 5/2 = y

More on Slopes

Page 68: 37 more on slopes-x

Two Facts About SlopesI. Parallel lines have the same slope.II. Slopes of perpendicular lines are the negative reciprocal of each other.Example C. a. The line L is parallel to 4x – 2y = 5, what is the slope of L? Solve for y for 4x – 2y = 5 4x – 5 = 2y 2x – 5/2 = y So the slope of 4x – 2y = 5 is 2.

More on Slopes

Page 69: 37 more on slopes-x

Two Facts About SlopesI. Parallel lines have the same slope.II. Slopes of perpendicular lines are the negative reciprocal of each other.Example C. a. The line L is parallel to 4x – 2y = 5, what is the slope of L? Solve for y for 4x – 2y = 5 4x – 5 = 2y 2x – 5/2 = y So the slope of 4x – 2y = 5 is 2. Since L is parallel to it , so L has slope 2 also.

More on Slopes

Page 70: 37 more on slopes-x

Two Facts About SlopesI. Parallel lines have the same slope.II. Slopes of perpendicular lines are the negative reciprocal of each other.Example C. a. The line L is parallel to 4x – 2y = 5, what is the slope of L? Solve for y for 4x – 2y = 5 4x – 5 = 2y 2x – 5/2 = y So the slope of 4x – 2y = 5 is 2. Since L is parallel to it , so L has slope 2 also.

More on Slopes

b. What is the slope of L if L is perpendicular to 3x = 2y + 4?

Page 71: 37 more on slopes-x

Two Facts About SlopesI. Parallel lines have the same slope.II. Slopes of perpendicular lines are the negative reciprocal of each other.Example C. a. The line L is parallel to 4x – 2y = 5, what is the slope of L? Solve for y for 4x – 2y = 5 4x – 5 = 2y 2x – 5/2 = y So the slope of 4x – 2y = 5 is 2. Since L is parallel to it , so L has slope 2 also.

More on Slopes

b. What is the slope of L if L is perpendicular to 3x = 2y + 4? Solve for y to find the slope of 3x – 4 = 2y

Page 72: 37 more on slopes-x

Two Facts About SlopesI. Parallel lines have the same slope.II. Slopes of perpendicular lines are the negative reciprocal of each other.Example C. a. The line L is parallel to 4x – 2y = 5, what is the slope of L? Solve for y for 4x – 2y = 5 4x – 5 = 2y 2x – 5/2 = y So the slope of 4x – 2y = 5 is 2. Since L is parallel to it , so L has slope 2 also.

More on Slopes

b. What is the slope of L if L is perpendicular to 3x = 2y + 4? Solve for y to find the slope of 3x – 4 = 2y x – 2 = y 2

3

Page 73: 37 more on slopes-x

Two Facts About SlopesI. Parallel lines have the same slope.II. Slopes of perpendicular lines are the negative reciprocal of each other.Example C. a. The line L is parallel to 4x – 2y = 5, what is the slope of L? Solve for y for 4x – 2y = 5 4x – 5 = 2y 2x – 5/2 = y So the slope of 4x – 2y = 5 is 2. Since L is parallel to it , so L has slope 2 also.

More on Slopes

b. What is the slope of L if L is perpendicular to 3x = 2y + 4? Solve for y to find the slope of 3x – 4 = 2y x – 2 = y Hence the slope of 3x = 2y + 4 is .

2 3

2 3

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Two Facts About SlopesI. Parallel lines have the same slope.II. Slopes of perpendicular lines are the negative reciprocal of each other.Example C. a. The line L is parallel to 4x – 2y = 5, what is the slope of L? Solve for y for 4x – 2y = 5 4x – 5 = 2y 2x – 5/2 = y So the slope of 4x – 2y = 5 is 2. Since L is parallel to it , so L has slope 2 also.

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b. What is the slope of L if L is perpendicular to 3x = 2y + 4? Solve for y to find the slope of 3x – 4 = 2y x – 2 = y Hence the slope of 3x = 2y + 4 is . So L has slope –2/3 since L is perpendicular to it.

2 3

2 3

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Summary on Slopes

How to Find SlopesI. If two points on the line are given, use the slope formula

II. If the equation of the line is given, solve for the y and get slope intercept form y = mx + b, then the number m is the slope.

Geometry of Slope The slope of tilted lines are nonzero. Lines with positive slopes connect quadrants I and III.Lines with negative slopes connect quadrants II and IV. Lines that have slopes with large absolute values are steep.The slope of a horizontal line is 0.A vertical lines does not have slope or that it’s UDF.Parallel lines have the same slopes.Perpendicular lines have the negative reciprocal slopes of each other.

riserun= m = Δy

Δxy2 – y1

x2 – x1=

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Exercise A. Identify the vertical and the horizontal lines by inspection first. Find their slopes or if it’s undefined, state so. Fine the slopes of the other ones by solving for the y.1. x – y = 3 2. 2x = 6 3. –y – 7= 0

4. 0 = 8 – 2x 5. y = –x + 4 6. 2x/3 – 3 = 6/5

7. 2x = 6 – 2y 8. 4y/5 – 12 = 3x/4 9. 2x + 3y = 3

10. –6 = 3x – 2y 11. 3x + 2 = 4y + 3x 12. 5x/4 + 2y/3 = 2 Exercise B. 13–18. Select two points and estimate the slope of each line.

13. 14. 15.

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16. 17. 18.Exercise C. Draw and find the slope of the line that passes through the given two points. Identify the vertical line and the horizontal lines by inspection first.19. (0, –1), (–2, 1) 20. (1, –2), (–2, 0) 21. (1, –2), (–2, –1)22. (3, –1), (3, 1) 23. (1, –2), (–2, 3) 24. (2, –1), (3, –1)25. (4, –2), (–3, 1) 26. (4, –2), (4, 0) 27. (7, –2), (–2, –6)28. (3/2, –1), (3/2, 1) 29. (3/2, –1), (1, –3/2)30. (–5/2, –1/2), (1/2, 1) 31. (3/2, 1/3), (1/3, 1/3)32. (–2/3, –1/4), (1/2, 2/3) 33. (3/4, –1/3), (1/3, 3/2)

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Exercise D. 34. Identify which lines are parallel and which one are perpendicular. A. The line that passes through (0, 1), (1, –2)

D. 2x – 4y = 1

B. C.

E. The line that’s perpendicular to 3y = xF. The line with the x–intercept at 3 and y intercept at 6. Find the slope, if possible of each of the following lines.35. The line passes with the x intercept at x = 2, and y–intercept at y = –5.

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36. The equation of the line is 3x = –5y+737. The equation of the line is 0 = –5y+7 38. The equation of the line is 3x = 739. The line is parallel to 2y = 5 – 6x 40. the line is perpendicular to 2y = 5 – 6x41. The line is parallel to the line in problem 30. 42. the line is perpendicular to line in problem 31.43. The line is parallel to the line in problem 33. 44. the line is perpendicular to line in problem 34.

More on SlopesFind the slope, if possible of each of the following lines