Learn on PengiBig Ideas Math, Algebra 2Chapter 1: Linear Functions

Lesson 2: Transformations of Linear and Absolute Value Functions

In this Grade 8 lesson from Big Ideas Math Algebra 2, Chapter 1, students learn how to apply transformations — including reflections in the x- and y-axis, horizontal and vertical stretches, and horizontal and vertical shrinks — to linear and absolute value functions. Students practice writing new function rules by multiplying inputs or outputs by specific values, such as replacing f(x) with -f(x) for an x-axis reflection or f(ax) for a horizontal shrink. The lesson builds toward combining multiple transformations to produce a single transformed function.

Section 1

Horizontal and Vertical Translations

Property

For any function f(x)f(x), the graph can be translated:

  1. Horizontal shift: The graph of g(x)=f(xh)g(x) = f(x-h) is the graph of f(x)f(x) shifted hh units horizontally.
  2. Vertical shift: The graph of g(x)=f(x)+kg(x) = f(x) + k is the graph of f(x)f(x) shifted kk units vertically.

Examples

Section 2

Reflection Across Y-Axis

Property

To reflect a function across the y-axis, replace xx with x-x in the function: y=f(x)y = f(-x)

Examples

Section 3

Reflection Across X-Axis: y = -f(x)

Property

To reflect a function across the x-axis, replace f(x)f(x) with f(x)-f(x):

y=f(x)y = -f(x)

This transformation multiplies every y-coordinate by 1-1 while keeping x-coordinates unchanged.

Section 4

Vertical Stretches and Shrinks of Functions

Property

The coefficient aa in the function f(x)=ag(x)f(x) = a \cdot g(x) affects the graph of g(x)g(x) by stretching or compressing it vertically.

  • If 0<a<10 < |a| < 1, the graph is compressed vertically (appears "wider" for parabolas).
  • If a>1|a| > 1, the graph is stretched vertically (appears "skinnier" for parabolas).
  • If aa is negative, the graph is also reflected across the x-axis.

Examples

Book overview

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Chapter 1: Linear Functions

  1. Lesson 1

    Lesson 1: Parent Functions and Transformations

  2. Lesson 2Current

    Lesson 2: Transformations of Linear and Absolute Value Functions

  3. Lesson 3

    Lesson 3: Modeling with Linear Functions

  4. Lesson 4

    Lesson 4: Solving Linear Systems

Lesson overview

Expand to review the lesson summary and core properties.

Expand

Section 1

Horizontal and Vertical Translations

Property

For any function f(x)f(x), the graph can be translated:

  1. Horizontal shift: The graph of g(x)=f(xh)g(x) = f(x-h) is the graph of f(x)f(x) shifted hh units horizontally.
  2. Vertical shift: The graph of g(x)=f(x)+kg(x) = f(x) + k is the graph of f(x)f(x) shifted kk units vertically.

Examples

Section 2

Reflection Across Y-Axis

Property

To reflect a function across the y-axis, replace xx with x-x in the function: y=f(x)y = f(-x)

Examples

Section 3

Reflection Across X-Axis: y = -f(x)

Property

To reflect a function across the x-axis, replace f(x)f(x) with f(x)-f(x):

y=f(x)y = -f(x)

This transformation multiplies every y-coordinate by 1-1 while keeping x-coordinates unchanged.

Section 4

Vertical Stretches and Shrinks of Functions

Property

The coefficient aa in the function f(x)=ag(x)f(x) = a \cdot g(x) affects the graph of g(x)g(x) by stretching or compressing it vertically.

  • If 0<a<10 < |a| < 1, the graph is compressed vertically (appears "wider" for parabolas).
  • If a>1|a| > 1, the graph is stretched vertically (appears "skinnier" for parabolas).
  • If aa is negative, the graph is also reflected across the x-axis.

Examples

Book overview

Jump across lessons in the current chapter without opening the full course modal.

Continue this chapter

Chapter 1: Linear Functions

  1. Lesson 1

    Lesson 1: Parent Functions and Transformations

  2. Lesson 2Current

    Lesson 2: Transformations of Linear and Absolute Value Functions

  3. Lesson 3

    Lesson 3: Modeling with Linear Functions

  4. Lesson 4

    Lesson 4: Solving Linear Systems