Math Problem Statement

If \( f(x) = -3 - 2x \) and \( g(x) = -\frac{x^2}{6} \), which of the following could not be in the range of \( f(g(x)) \)? Options: A. -4 B. -2 C. 0 D. 2

Solution

To solve the problem, we need to find the range of f(g(x))f(g(x)) and determine which of the options cannot be in this range.

Given functions:

  1. f(x)=32xf(x) = -3 - 2x
  2. g(x)=x26g(x) = -\frac{x^2}{6}

Step 1: Determine f(g(x))f(g(x))

Substitute g(x)g(x) into f(x)f(x): f(g(x))=f(x26)f(g(x)) = f\left(-\frac{x^2}{6}\right) Using the definition of f(x)=32xf(x) = -3 - 2x, replace xx in f(x)f(x) with x26-\frac{x^2}{6}: f(x26)=32(x26)f\left(-\frac{x^2}{6}\right) = -3 - 2\left(-\frac{x^2}{6}\right) =3+x23= -3 + \frac{x^2}{3}

Step 2: Determine the Range of f(g(x))f(g(x))

Since f(g(x))=3+x23f(g(x)) = -3 + \frac{x^2}{3}, analyze x23\frac{x^2}{3}:

  • x2x^2 is always non-negative, so x230\frac{x^2}{3} \geq 0.
  • Therefore, 3+x233-3 + \frac{x^2}{3} \geq -3.

The range of f(g(x))f(g(x)) is [3,)[-3, \infty).

Step 3: Determine Which Option is Not in the Range

Looking at the options:

  • A. -4: This is outside the range [3,)[-3, \infty).
  • B. -2: This is within the range.
  • C. 0: This is within the range.
  • D. 2: This is within the range.

Conclusion

The value that could not be in the range of f(g(x))f(g(x)) is: A. -4

Would you like further details or have any questions?

Here are five related questions to expand your understanding:

  1. How would the solution change if f(x)f(x) or g(x)g(x) were modified?
  2. What would be the range if g(x)g(x) were a linear function instead?
  3. How does the domain of g(x)g(x) affect the possible values for f(g(x))f(g(x))?
  4. Can you find a different function pair where a specific output is excluded from f(g(x))f(g(x))?
  5. How does composition of functions affect the range in general?

Tip: When analyzing composite functions, start by focusing on the range of the inner function to help determine the output possibilities for the overall composition.

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Math Problem Analysis

Mathematical Concepts

Function Composition
Quadratic Functions
Range of Functions

Formulas

f(x) = -3 - 2x
g(x) = -\frac{x^2}{6}
f(g(x)) = -3 + \frac{x^2}{3}

Theorems

Range determination in composite functions

Suitable Grade Level

Grades 10-12