Graph the Transformations of Absolute Value Functions

Algebra-2

1. Fundamental Concepts

  • Parent Function: The basic absolute value function is . Its graph is a V-shape with the vertex at the origin , opening upwards.
  • Transformations: Changes made to the parent function that alter its graph, including translations (shifts), stretches, compressions, and reflections.

2. Key Concepts

Transformations of the absolute value function are based on the general form , where:
  • a: Controls vertical stretch, compression, or reflection.
    • If : Vertical stretch (narrower than the parent function).
    • If : Vertical compression (wider than the parent function).
    • If : Reflection over the x-axis (opens downward).
  • h: Controls horizontal translation (shift along the x-axis).
    • If : Shift right by h units.
    • If : Shift left by  units (equivalent to ).
  • k: Controls vertical translation (shift along the y-axis).
    • If : Shift up by k units.
    • If : Shift down by  units (equivalent to ).
  • Reflection over the y-axis: Represented by , which is equivalent to  (since absolute value eliminates the sign, the graph remains unchanged).

3. Examples

Easy: Identify Transformations

Describe the transformations of  to .
Solution: The parent function  is shifted right by 2 units () and up by 3 units ().

Medium: Graph a Transformed Function

Graph  using transformations of .
Solution:
  1. Start with  (vertex at ).
  2. Shift left by 1 unit:  (vertex at ).
  3. Vertically stretch by a factor of 2:  (narrower V-shape).
  4. Shift down by 1 unit:  (vertex at , opens upward).

4. Problem-Solving Techniques

  • Identify the Vertex: For a transformed absolute value function, the vertex  is the starting point for analyzing shifts. It can be directly read from the graph or the equation.
  • Determine a: Check if the graph opens up () or down (). Compare the "width" to the parent function: narrower means  (stretch), wider means  (compression).
  • Reverse-Engineer Equations from Graphs:
    1. Locate the vertex  from the graph.
    2. Determine the direction of opening and stretch/compression to find a.
    3. Substitute ah, and k into .
  • Graph Step-by-Step: Start with the parent function , apply horizontal/vertical shifts first, then stretch/compression, and finally reflections (order ensures accuracy).