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Select the correct answer.

Consider these functions:

[tex]\[
\begin{array}{l}
f(x)=-\frac{1}{2} x^2 + 5x \\
g(x) = x^2 + 2
\end{array}
\][/tex]

What is the value of [tex]\( f(g(-2)) \)[/tex]?

A. -28
B. -12
C. 12
D. 146


Sagot :

To solve for [tex]\( f(g(-2)) \)[/tex] using the given functions [tex]\( f(x) \)[/tex] and [tex]\( g(x) \)[/tex], follow these steps:

1. Evaluate [tex]\( g(-2) \)[/tex]:
The function [tex]\( g(x) \)[/tex] is given by:
[tex]\[ g(x) = x^2 + 2 \][/tex]
Substituting [tex]\( x = -2 \)[/tex] into the function:
[tex]\[ g(-2) = (-2)^2 + 2 = 4 + 2 = 6 \][/tex]

2. Evaluate [tex]\( f(g(-2)) \)[/tex]:
We now know that [tex]\( g(-2) = 6 \)[/tex]. Next, we need to find [tex]\( f(6) \)[/tex] using the function [tex]\( f(x) \)[/tex], which is given by:
[tex]\[ f(x) = -\frac{1}{2} x^2 + 5 x \][/tex]
Substituting [tex]\( x = 6 \)[/tex] into the function:
[tex]\[ f(6) = -\frac{1}{2} (6)^2 + 5 \cdot 6 \][/tex]
Calculate [tex]\( 6^2 \)[/tex]:
[tex]\[ 6^2 = 36 \][/tex]
Then:
[tex]\[ f(6) = -\frac{1}{2} \cdot 36 + 5 \cdot 6 = -18 + 30 = 12 \][/tex]

3. Conclusion:
Therefore, the value of [tex]\( f(g(-2)) \)[/tex] is:
[tex]\[ \boxed{12} \][/tex]

Hence, the correct answer is:
C. 12