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

we'll follow these steps:

1. First, evaluate [tex]\( g(-2) \)[/tex].

[tex]\[ g(x) = x^2 + 2 \][/tex]
[tex]\[ g(-2) = (-2)^2 + 2 = 4 + 2 = 6 \][/tex]

So, [tex]\( g(-2) = 6 \)[/tex].

2. Next, with this result, we need to find [tex]\( f(g(-2)) \)[/tex], which is [tex]\( f(6) \)[/tex].

[tex]\[ f(x) = -\frac{1}{2} x^2 + 5 x \][/tex]
[tex]\[ f(6) = -\frac{1}{2} (6)^2 + 5(6) \][/tex]
Calculate [tex]\( 6^2 \)[/tex]:

[tex]\[ 6^2 = 36 \][/tex]

Now substitute [tex]\( 36 \)[/tex] into the equation:

[tex]\[ f(6) = -\frac{1}{2} (36) + 5(6) = -18 + 30 \][/tex]

Finally, sum the results:

[tex]\[ -18 + 30 = 12 \][/tex]

So, [tex]\( f(g(-2)) = 12 \)[/tex].

Therefore, the correct answer is:
[tex]\[ \boxed{12} \][/tex]