Question

Difficulty: MediumFunction Evaluation, Composition, and Properties

The functions ff and gg are defined for all real numbers by f(x)=2x5f(x) = 2x - 5 and g(x)=(x+3)2g(x) = (x + 3)^2. What is the value of f(g(1))f(g(-1))?

  1. A
    15
  2. B
    16
  3. 3Answer
  4. D
    27
  5. E
    -28

Answer

3
To evaluate the composite function f(g(1))f(g(-1)), first evaluate the inner function g(1)=(1+3)2=4g(-1) = (-1 + 3)^2 = 4. Then, substitute this result into the outer function to get f(4)=2(4)5=3f(4) = 2(4) - 5 = 3.

Step-by-Step Solution

1
Evaluate the inner function g(x)g(x) at x=1x = -1.
g(1)=4g(-1) = 4
In the composition f(g(1))f(g(-1)), the inner function must be evaluated first. Substituting 1-1 into g(x)=(x+3)2g(x) = (x + 3)^2 gives g(1)=(1+3)2=22=4g(-1) = (-1 + 3)^2 = 2^2 = 4.
2
Evaluate the outer function f(x)f(x) at the output of the inner function.
f(4)=3f(4) = 3
Substitute the output g(1)=4g(-1) = 4 into f(x)=2x5f(x) = 2x - 5, which yields f(4)=2(4)5=85=3f(4) = 2(4) - 5 = 8 - 5 = 3.

Key Concept

Function Composition and Evaluation
Estimated Time:1m 0s
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