1.11.1 functions. quick review what you’ll learn about numeric models algebraic models graphic...
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1.11.11.11.1
FunctionsFunctions
Quick Review 2
2
2
2
4 2
Factor the following expressions completely over the real numbers.
1. 9
2. 4 81
3. 8 16
4. 2 7 3
5. 3 4
x
y
x x
x x
x x
What you’ll learn about• Numeric Models• Algebraic Models• Graphic Models• The Zero Factor Property• Problem Solving• Grapher Failure and Hidden Behavior• A Word About Proof
… and whyNumerical, algebraic, and graphical models provide
differentmethods to visualize, analyze, and understand data.
Mathematical ModelA mathematical model is a mathematical
structure that approximates phenomena for the
purpose of studying or predicting their behavior.
Numeric ModelA numeric model is a kind of mathematicalmodel in which numbers (or data) are analyzed to gain insights into phenomena.
Algebraic ModelAn algebraic model uses formulas to relatevariable quantities associated with thephenomena being studied.
Example Comparing Pizzas
A pizzeria sells a rectangular 20" by 22" pizza for the same price as its
large round pizza (24" diameter). If both pizzas are the same thickness,
which option gives the most pizza for the money?
Example Comparing Pizzas
A pizzeria sells a rectangular 20" by 22" pizza for the same price as its
large round pizza (24" diameter). If both pizzas are the same thickness,
which option gives the most pizza for the money?
2
2
Compare the areas of the pizzas.
Rectangular pizza: Area 20 22 440 square inches
24Circular pizza: Area 144 452.4 square inches
2
The round pizza is larger and therefore gives more for t
l w
r
he money.
Graphical ModelA graphical model is a visible
representation of a numerical model or an algebraic model thatgives insight into the relationships betweenvariable quantities.
Example Solving an Equation
2Solve the equation 8 4 algebraically.x x
Example Solving an Equation
2Solve the equation 8 4 algebraically.x x
2
Set the given equation equal to zero:
4 8 0
Use the quadratic formula to solve for .
4 16 32
2
4 48
2
4 4 3
2
2 2 3
Approximations for the solutions are 1.4641 and -5.4641.
x x
x
x
x x
Fundamental Connection
If is a real number that solves the equation ( ) 0, then these three
statements are equivalent:
1. The number is a root (or solution) of the equation ( ) 0.
2. The number is a zero of ( ).
3. T
a f x
a f x
a y f x
he number is an -intercept of the graph of ( ).a x y f x
Pólya’s Four Problem-Solving Steps
1. Understand the problem.2. Devise a plan.3. Carry out the plan.4. Look back.
A Problem-Solving Process
Step 1 – Understand the problem.• Read the problem as stated, several
times if necessary.• Be sure you understand the meaning of
each term used.• Restate the problem in your own words.
Discuss the problem with others if you can.
• Identify clearly the information that you need to solve the problem.
• Find the information you need from the given data.
A Problem-Solving Process
Step 2 – Develop a mathematical model of the problem.
• Draw a picture to visualize the problem situation. It usually helps.
• Introduce a variable to represent the quantity you seek.
• Use the statement of the problem to find an equation or inequality that relates the variables you seek to quantities that you know.
A Problem-Solving Process
Step 3 – Solve the mathematical model and support or confirm the solution.
• Solve algebraically using traditional algebraic models and support graphically or support numerically using a graphing utility.
• Solve graphically or numerically using a graphing utility and confirm algebraically using traditional algebraic methods.
• Solve graphically or numerically because there is no other way possible.
A Problem-Solving Process
Step 4 – Interpret the solution in the problem setting.
• Translate your mathematical result into the problem setting and decide whether the result makes sense.
Example Seeing Grapher Failure
Look at the graph of 3 /(2 5) on a graphing calculator.
Is there an -intercept?
y x
x
Example Seeing Grapher Failure
Look at the graph of 3 /(2 5) on a graphing calculator.
Is there an -intercept?
y x
x
The graph is shown below. Notice that the graph appears to show an
-intercept between 2 and 3. Confirm this algebraically:
30
2 50 2 5 3
0 3 This statement is false for all , so there is no -inte
x
xx
x x
rcept.
The grapher plots points at regular increments from left to right,
connecting the points as it goes.
1.1(a)/1.21.1(a)/1.21.1(a)/1.21.1(a)/1.2
Functions and Their PropertiesFunctions and Their Properties
Quick Review
2
2
Solve the equation or inequality.
1. 9 0
2. 16 0
Find all values of algebraically for which the algebraic
expression is not defined.
13.
3
4. 3
15.
3
x
x
x
x
x
x
x
What you’ll learn about• Function Definition and Notation• Domain and Range• Continuity• Increasing and Decreasing Functions• Boundedness• Local and Absolute Extrema• Symmetry• Asymptotes• End Behavior
… and whyFunctions and graphs form the basis for understanding The mathematics and applications you will see both in your
work place and in coursework in college.
Function, Domain, and Range
A function from a set D to a set R is a rule that
assigns to every element in D a unique element
in R. The set D of all input values is the domain
of the function, and the set R of all output values
is the range of the function.
Mapping
Example Seeing a Function Graphically
Of the three graphs shown below, which is not the graph of a function?
Example Seeing a Function Graphically
Of the three graphs shown below, which is not the graph of a function?
The graph in (c) is not the graph of a function. There are three points on the graph with x-coordinates 0.
Vertical Line TestA graph (set of points (x,y)) in the
xy-planedefines y as a function of x if and
only if no vertical line intersects the graph in
more than onepoint.
Agreement
Unless we are dealing with a model that
necessitates a restricted domain, we will assume that the domain of a function defined by an algebraic expression is the same as the domain of the algebraic expression, the implied domain.
For models, we will use a domain that fits the situation, the relevant domain.
Example Finding the Domain of a Function
Find the domain of the function.
( ) 2f x x
Example Finding the Domain of a
Function
Find the domain of the function.
( ) 2f x x
Solve algebraically:
The expression under a radical may not be negative.
2 0
2
The domain of is the interval [ 2, ).
x
x
f
Example Finding the Range of a Function
2Find the range of the function ( ) .f x
x
Example Finding the Range of a Function
2
Find the range of the function ( ) .f xx
Solve Graphically:
2The graph of shows that the range is all real numbers except 0.
The range in interval notation is ,0 0, .
yx
Continuity
Example Identifying Points of Discontinuity
Which of the following figures shows functions that are
discontinuous at x = 2?
Example Identifying Points of Discontinuity
Which of the following figures shows functions that are
discontinuous at x = 2?
The function on the right is not defined at x = 2 and can not be continuous there. This is a removable discontinuity.
Increasing and Decreasing Functions
Increasing, Decreasing, and Constant Function
on an IntervalA function f is increasing on an interval if, for
any two points in the interval, a positive change in x results in a positive change in f(x).
A function f is decreasing on an interval if, for any two points in the interval, a positive change in x results in a negative change in f(x).
A function f is constant on an interval if, for any two points in the interval, a positive change in x results in a zero change in f(x).
Example Analyzing a Function for
Increasing-Decreasing Behavior2
2Given ( ) . Tell the intervals on which ( ) is increasing and the
1intervals on which it is decreasing.
xg x g x
x
Example Analyzing a Function for
Increasing-Decreasing Behavior
2
2Given ( ) . Tell the intervals on which ( ) is increasing and the
1intervals on which it is decreasing.
xg x g x
x
From the graph, we see that ( ) is increasing on , 1 , increasing on
( 1,0], decreasing on [0,1), and decreasing on (1, ).
g x
Lower Bound, Upper Bound and Bounded
A function f is bounded below of there is somenumber b that is less than or equal to everynumber in the range of f. Any such number b iscalled a lower bound of f.
A function f is bounded above of there is somenumber B that is greater than or equal to everynumber in the range of f. Any such number B iscalled a upper bound of f.
A function f is bounded if it is bounded both above and below.
Local and Absolute Extrema
A local maximum of a function f is a value f(c) that is greater than or equal to all range values of f on some open interval containing c. If f(c) is greater than or equal to all range values of f, then f(c) is the maximum (or absolute maximum) value of f.
A local minimum of a function f is a value f(c) that is less than or equal to all range values of f on some open interval containing c. If f(c) is less than or equal to all range values of f, then f(c) is the minimum (or absolute minimum) value of f.
Local extrema are also called relative extrema.
Example Identifying Local Extrema
4 2Find the local maxima or local minima of ( ) 7 6 . Find the
values of where each local maximum and local minimum occurs.
f x x x x
x
Example Identifying Local Extrema
4 2Find the local maxima or local minima of ( ) 7 6 . Find the
values of where each local maximum and local minimum occurs.
f x x x x
x
The graph of the function suggests that there are two local minimum value and
one local maximum value. Use the calculator to approximate local minima as
-24.06 (which occurs at -2.06) and -1.77 (whicx h occurs at 1.60). The
local maximum is 1.32 (which occurs at 0.46).
x
x
Symmetry with respect to the y-axis
Symmetry with respect to the x-axis
Symmetry with respect to the origin
Example Checking Functions for
Symmetry2
Tell whether the following function is odd, even, or neither.
( ) 3f x x
Example Checking Functions for
Symmetry 2
Tell whether the following function is odd, even, or neither.
( ) 3f x x
2
2
Solve Algebraically:
Find (- ).
(- ) (- ) 3
3
( ) The function is even.
f x
f x x
x
f x
Horizontal and Vertical Asymptotes
The line is a horizontal asymptote of the graph of a function ( )
if ( ) approaches a limit of as approaches + or - .
In limit notation: lim ( ) or lim ( ) .
The line is a ver
x x
y b y f x
f x b x
f x b f x b
x a
tical asymptote of the graph of a function ( )
if ( ) approaches a limit of + or - as approaches from either
direction.
In limit notation: lim ( ) or lim ( ) .x a x a
y f x
f x x a
f x f x