1.

1 Parent Functions and Transformations

Essential Question What are the characteristics of some of the
COMMON basic parent functions?
CORE
Learning Standard
HSF-BF.B.3
Identifying Basic Parent Functions

Work with a partner. Graphs of eight basic parent functions are shown below.
Classify each function as constant, linear, absolute value, quadratic, square root,
cubic, reciprocal, or exponential. Justify your reasoning.
JUSTIFYING a. 4 b. 4
CONCLUSIONS
To be proficient in math,
you need to justify −6 6 −6 6

your conclusions and

communicate them
clearly to others. −4 −4

c. 4 d. 4

−6 6 −6 6

−4 −4

e. 4 f. 4

−6 6 −6 6

−4 −4

g. 4 h. 4

−6 6 −6 6

−4 −4

Communicate Your Answer

2. What are the characteristics of some of the basic parent functions?

3. Write an equation for each function whose graph is shown in Exploration 1.

Then use a graphing calculator to verify that your equations are correct.

Section 1.1 Parent Functions and Transformations 3

1.1 Lesson What You Will Learn
Identify families of functions.
Describe transformations of parent functions.
Core Vocabul
Vocabulary
larry Describe combinations of transformations.
parent function, p. 4
transformation, p. 5
translation, p. 5
Identifying Function Families
reflection, p. 5 Functions that belong to the same family share key characteristics. The parent
vertical stretch, p. 6 function is the most basic function in a family. Functions in the same family are
transformations of their parent function.
vertical shrink, p. 6
Previous
function Core Concept
domain
Parent Functions
range
slope Family Constant Linear Absolute Value Quadratic
scatter plot Rule f(x) = 1 f(x) = x f(x) = ∣ x ∣ f(x) = x 2
Graph y y y y

x x
x x

Domain All real numbers All real numbers All real numbers All real numbers
Range y=1 All real numbers y≥0 y≥0

LOOKING FOR Identifying a Function Family

STRUCTURE
Identify the function family to which f belongs. y
You can also use function
Compare the graph of f to the graph of its
rules to identify functions. 6
parent function.
The only variable term in
f is an ∣ x ∣-term, so it is an SOLUTION 4
absolute value function.
The graph of f is V-shaped, so f is an absolute
value function.
f(x) = 2x + 1
The graph is shifted up and is narrower than
−4 −2 2 4 x
the graph of the parent absolute value function.
The domain of each function is all real numbers,
but the range of f is y ≥ 1 and the range of the
parent absolute value function is y ≥ 0.

Monitoring Progress Help in English and Spanish at BigIdeasMath.com

1. Identify the function family to which 1

g(x) = 4 (x − 3)2
g belongs. Compare the graph of g to y
6
the graph of its parent function.
4

2 4 6 x

4 Chapter 1 Linear Functions

 Describing Transformations
A transformation changes the size, shape, position, or orientation of a graph.
A translation is a transformation that shifts a graph horizontally and/or vertically
but does not change its size, shape, or orientation.

REMEMBER
Graphing and Describing Translations
The slope-intercept form
of a linear equation is
Graph g(x) = x − 4 and its parent function. Then describe the transformation.
y = mx + b, where m is
the slope and b is the SOLUTION
y-intercept.
The function g is a linear function with a slope y
of 1 and a y-intercept of −4. So, draw a line 2

through the point (0, −4) with a slope of 1.

The graph of g is 4 units below the graph of −4 −2 2 4 x
the parent linear function f. f(x) = x −2

So, the graph of g(x) = x − 4 is a vertical (0, −4)

translation 4 units down of the graph of g(x) = x − 4
the parent linear function. −6

A reflection is a transformation that flips a graph over a line called the line of
reflection. A reflected point is the same distance from the line of reflection as the
original point but on the opposite side of the line.

Graphing and Describing Reflections

REMEMBER Graph p(x) = −x 2 and its parent function. Then describe the transformation.
The function p(x) = −x 2
is written in function SOLUTION
notation, where p(x) is The function p is a quadratic function. Use a table of values to graph each function.
another name for y.
y
x y = x2 y = −x 2 4

−2 4 −4
2
−1 1 −1 f(x) = x2
0 0 0 −4 −2 2 4 x
1 1 −1 p(x) = −x2 −2
2 4 −4
−4

The graph of p is the graph of the parent function flipped over the x-axis.

So, p(x) = −x 2 is a reflection in the x-axis of the parent quadratic function.

Monitoring Progress Help in English and Spanish at BigIdeasMath.com

Graph the function and its parent function. Then describe the transformation.

2. g(x) = x + 3 3. h(x) = (x − 2)2 4. n(x) = −∣ x ∣

Section 1.1 Parent Functions and Transformations 5

 Another way to transform the graph of a function is to multiply all of the y-coordinates
by the same positive factor (other than 1). When the factor is greater than 1, the
transformation is a vertical stretch. When the factor is greater than 0 and less than 1,
it is a vertical shrink.

Graphing and Describing Stretches and Shrinks

Graph each function and its parent function. Then describe the transformation.

a. g(x) = 2 ∣ x ∣ b. h(x) = —12 x2

SOLUTION
a. The function g is an absolute value function. Use a table of values to graph
the functions.
g(x) = 2x
x y = ∣x∣ y = 2∣ x ∣ y

−2 2 4 6
−1 1 2
4
0 0 0
REASONING 1 1 2 2
ABSTRACTLY 2 2 4 f(x) = x
To visualize a vertical −4 −2 2 4 x
stretch, imagine pulling
the points away from
the x-axis. The y-coordinate of each point on g is two times the y-coordinate of the
corresponding point on the parent function.
So, the graph of g(x) = 2∣ x ∣ is a vertical stretch of the graph of the parent
absolute value function.
b. The function h is a quadratic function. Use a table of values to graph
the functions.
f(x) = x2
y
x y = x2 y = —12 x 2
To visualize a vertical 6
−2 4 2
shrink, imagine pushing
the points toward −1 1 1
—2 4
the x-axis.
0 0 0
2
1
1 1 1
—2 h(x) = 2 x 2

2 4 2 −4 −2 2 4 x

The y-coordinate of each point on h is one-half of the y-coordinate of the

corresponding point on the parent function.

So, the graph of h(x) = —12 x 2 is a vertical shrink of the graph of the parent
quadratic function.

Monitoring Progress Help in English and Spanish at BigIdeasMath.com

Graph the function and its parent function. Then describe the transformation.

7. c(x) = 0.2∣ x ∣
3
5. g(x) = 3x 6. h(x) = —2 x2

6 Chapter 1 Linear Functions

 Combinations of Transformations
You can use more than one transformation to change the graph of a function.

Describing Combinations of Transformations

Use a graphing calculator to graph g(x) = −∣ x + 5 ∣ − 3 and its parent function. Then
describe the transformations.

SOLUTION 8

The function g is an absolute value function. f

−12
The graph shows that g(x) = −∣ x + 5 ∣ − 3
10

is a reflection in the x-axis followed by a g

translation 5 units left and 3 units down of the
graph of the parent absolute value function. −10

Modeling with Mathematics

Time Height The table shows the height y of a dirt bike x seconds after jumping off a ramp. What
(seconds), x (feet), y type of function can you use to model the data? Estimate the height after 1.75 seconds.
0 8 SOLUTION
0.5 20
1. Understand the Problem You are asked to identify the type of function that can
1 24 model the table of values and then to find the height at a specific time.
1.5 20 2. Make a Plan Create a scatter plot of the data. Then use the relationship shown in
2 8 the scatter plot to estimate the height after 1.75 seconds.
3. Solve the Problem Create a scatter plot. y
30
The data appear to lie on a curve that resembles
a quadratic function. Sketch the curve.
20
So, you can model the data with a quadratic
function. The graph shows that the height is 10
about 15 feet after 1.75 seconds.
0
0 1 2 3 x

4.
4 Look Back To check that your solution is reasonable, analyze the values in the
table. Notice that the heights decrease after 1 second. Because 1.75 is between
1.5 and 2, the height must be between 20 feet and 8 feet.

8 < 15 < 20 ✓

Help in English and Spanish at BigIdeasMath.com

U a graphing calculator to graph the function and its parent function.

Use
Then describe the transformations.
T
1
8. h(x) = −—4 x + 5 9. d(x) = 3(x − 5)2 − 1

10. The table shows the amount of fuel in a chainsaw over time. What type of
function can you use to model the data? When will the tank be empty?

Time (minutes), x 0 10 20 30 40
Fuel remaining (fluid ounces), y 15 12 9 6 3

Section 1.1 Parent Functions and Transformations 7

 1.1 Exercises Dynamic Solutions available at BigIdeasMath.com

Vocabulary and Core Concept Check

1. COMPLETE THE SENTENCE The function f(x) = x 2 is the ______ of f(x) = 2x 2 − 3.

2. DIFFERENT WORDS, SAME QUESTION Which is different? Find “both” answers.

What are the vertices of the figure after a y

4
reflection in the x-axis, followed by a translation
2 units right? 2

What are the vertices of the figure after a

−4 −2 2 4 x
translation 6 units up and 2 units right?
−2

What are the vertices of the figure after

a translation 2 units right, followed by a −4

reflection in the x-axis?

What are the vertices of the figure after a

translation 6 units up, followed by a reflection
in the x-axis?

Monitoring Progress and Modeling with Mathematics

In Exercises 3–6, identify the function family to which 7. MODELING WITH MATHEMATICS At 8:00 a.m.,
f belongs. Compare the graph of f to the graph of its the temperature is 43°F. The temperature increases
parent function. (See Example 1.) 2°F each hour for the next 7 hours. Graph the
temperatures over time t (t = 0 represents 8:00 a.m.).
3. 4.
What type of function can you use to model the data?
y y
Explain.
−4 −2 x
−2 8. MODELING WITH MATHEMATICS You purchase a
−4 −2 2 4x car from a dealership for $10,000. The trade-in value
−4
−2 of the car each year after the purchase is given by
the function f(x) = 10,000 − 250x 2. What type of
function can you use to model the data?
f(x) = −2x2 + 3
f(x) = 2x + 2 − 8 In Exercises 9–18, graph the function and its parent
5. 6. function. Then describe the transformation. (See
Examples 2 and 3.)
y y
20 6
9. g(x) = x + 4 10. f(x) = x − 6
f(x) = 3
10 4
11. f(x) = x 2 − 1 12. h(x) = (x + 4)2
2
−2 2 4 6x
13. g(x) = ∣ x − 5 ∣ 14. f(x) = 4 + ∣ x ∣
f(x) = 5x − 2 −4 −2 2 4x
−20 −2 15. h(x) = −x 2 16. g(x) = −x

17. f(x) = 3 18. f(x) = −2

8 Chapter 1 Linear Functions

HSCC_Alg2_PE_01.01.indd 8 5/28/14 11:44 AM

In Exercises 19–26, graph the function and its parent MATHEMATICAL CONNECTIONS In Exercises 37 and 38,
function. Then describe the transformation. find the coordinates of the figure after the
(See Example 4.) transformation.
1
19. f(x) = —3 x 20. g(x) = 4x 37. Translate 2 units 38. Reflect in the x-axis.
down.
1
21. f(x) = 2x2 22. h(x) = —3 x2
y y
4 4
3 4 A B
23. h(x) = —4 x 24. g(x) = —3 x
2
A
25. h(x) = 3∣ x ∣ 26. f(x) = —2 ∣ x ∣
1
D C
−4 −2 4x −4 −2 2 4x
B −2
In Exercises 27–34, use a graphing calculator to graph
the function and its parent function. Then describe the −4
C
−4
transformations. (See Example 5.)
27. f(x) = 3x + 2 28. h(x) = −x + 5
USING TOOLS In Exercises 39–44, identify the function
family and describe the domain and range. Use a
29. h(x) = −3∣ x ∣ − 1 30. f(x) = —4 ∣ x ∣ + 1
3
graphing calculator to verify your answer.
39. g(x) = ∣ x + 2 ∣ − 1 40. h(x) = ∣ x − 3 ∣ + 2
1
31. g(x) = —2 x2 − 6 32. f(x) = 4x2 − 3

33. f(x) = −(x + 3)2 + —4

1
41. g(x) = 3x + 4 42. f(x) = −4x + 11

34. g(x) = −∣ x − 1 ∣ − —2 43. f(x) = 5x 2 − 2 44. f(x) = −2x2 + 6

1

45. MODELING WITH MATHEMATICS The table shows

ERROR ANALYSIS In Exercises 35 and 36, identify and the speeds of a car as it travels through an intersection
correct the error in describing the transformation of the with a stop sign. What type of function can you use to
parent function. model the data? Estimate the speed of the car when it

✗
35. is 20 yards past the intersection. (See Example 6.)
y

−4 −2 2 4x Displacement from Speed

−4 sign (yards), x (miles per hour), y
−100 40
−8
−50 20
−12
−10 4
The graph is a reflection in the x-axis 0 0
and a vertical shrink of the parent 10 4
quadratic function.
50 20
100 40
36.
✗ 4
y

46. THOUGHT PROVOKING In the same coordinate plane,

sketch the graph of the parent quadratic function
2
and the graph of a quadratic function that has no
x-intercepts. Describe the transformation(s) of the
2 4 6 x parent function.

The graph is a translation 3 units right of

the parent absolute value function, so the 47. USING STRUCTURE Graph the functions
function is f(x) = ∣ x + 3 ∣. f(x) = ∣ x − 4 ∣ and g(x) = ∣ x ∣ − 4. Are they
equivalent? Explain.

Section 1.1 Parent Functions and Transformations 9

48. HOW DO YOU SEE IT? Consider the graphs of f, g, 51. PROBLEM SOLVING You are playing basketball with
and h. your friends. The height (in feet) of the ball above the
ground t seconds after a shot is made is modeled by
h 4 y the function f(t) = −16t 2 + 32t + 5.2.
f
g a. Without graphing, identify the type of function
2
that models the height of the basketball.
−4 2 4x
b. What is the value of t when the ball is released
from your hand? Explain your reasoning.
−2
c. How many feet above the ground is the ball when
−4 it is released from your hand? Explain.

a. Does the graph of g represent a vertical stretch 52. MODELING WITH MATHEMATICS The table shows the
or a vertical shrink of the graph of f ? Explain battery lives of a computer over time. What type of
your reasoning. function can you use to model the data? Interpret the
meaning of the x-intercept in this situation.
b. Describe how to transform the graph of f to obtain
the graph of h.
Time Battery life
(hours), x remaining, y
49. MAKING AN ARGUMENT Your friend says two 1 80%
different translations of the graph of the parent linear 3 40%
function can result in the graph of f(x) = x − 2. Is
your friend correct? Explain. 5 0%
6 20%
50. DRAWING CONCLUSIONS A person swims at a 8 60%
constant speed of 1 meter per second. What type
of function can be used to model the distance the
swimmer travels? If the person has a 10-meter head 53. REASONING Compare each function with its parent
start, what type of transformation does this function. State whether it contains a horizontal
represent? Explain. translation, vertical translation, both, or neither.
Explain your reasoning.
a. f(x) = 2∣ x ∣ − 3 b. f(x) = (x − 8)2
c. f(x) = ∣ x + 2 ∣ + 4 d. f(x) = 4x 2

54. CRITICAL THINKING Use the values −1, 0, 1,

and 2 in the correct box so the graph of each function
intersects the x-axis. Explain your reasoning.

a. f(x) = 3x +1 b. f(x) = ∣ 2x − 6 ∣ −
c. f(x) = x2 + 1 d. f(x) =

Maintaining Mathematical Proficiency Reviewing what you learned in previous grades and lessons

Determine whether the ordered pair is a solution of the equation. (Skills Review Handbook)
55. f(x) = ∣ x + 2 ∣; (1, −3) 56. f(x) = ∣ x ∣ − 3; (−2, −5)

57. f(x) = x − 3; (5, 2) 58. f(x) = x − 4; (12, 8)

Find the x-intercept and the y-intercept of the graph of the equation. (Skills Review Handbook)
59. y=x 60. y=x+2

61. 3x + y = 1 62. x − 2y = 8

10 Chapter 1 Linear Functions