Math Problem Statement

Write the following as a piecewise function. f(x) = -|x + 4|

Solution

To convert the function f(x)=x+4f(x) = -|x + 4| into a piecewise function, we need to consider the behavior of the absolute value expression x+4|x + 4|. The absolute value causes the function to have different expressions depending on whether the input expression inside the absolute value is positive or negative.

  1. Identify critical point: The absolute value changes expression at the point where x+4=0x + 4 = 0. Solving for xx, we get x=4x = -4.

  2. Define expressions on each interval:

    • When x+40x + 4 \geq 0 (i.e., x4x \geq -4), the expression inside the absolute value is non-negative. So, x+4=x+4|x + 4| = x + 4.
    • When x+4<0x + 4 < 0 (i.e., x<4x < -4), the expression inside the absolute value is negative. Thus, x+4=(x+4)=x4|x + 4| = -(x + 4) = -x - 4.
  3. Piecewise function: We can now write f(x)f(x) as:

    - (x + 4) & \text{if } x \geq -4 \\ - (-x - 4) & \text{if } x < -4 \end{cases}$$ Simplifying each case: $$f(x) = \begin{cases} -x - 4 & \text{if } x \geq -4 \\ x + 4 & \text{if } x < -4 \end{cases}$$

This piecewise representation accurately reflects the original function but splits it into two linear expressions based on the value of xx relative to the critical point 4-4.

Would you like further details or have any other questions on this topic? Here are some possible follow-up questions:

  1. How can we graph the function f(x)=x+4f(x) = -|x + 4|?
  2. What are the properties of this function such as domain, range, and intercepts?
  3. How does the behavior of the function change at x=4x = -4?
  4. Can we derive similar piecewise functions for other absolute value expressions?
  5. How do we verify this piecewise function matches the original function?

Tip: When dealing with absolute value functions, always check for points where the expression inside the absolute value equals zero, as these points often define where the function changes its behavior.

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Math Problem Analysis

Mathematical Concepts

Absolute Value Functions
Piecewise Functions
Linear Equations

Formulas

|x + 4|
Piecewise function definition

Theorems

Properties of Absolute Value Functions

Suitable Grade Level

Grades 9-11