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Select the correct answer.

Consider these functions:

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

What is the value of [tex]\( g(f(-1)) \)[/tex]?

A. 2
B. 8
C. 22
D. 48


Sagot :

To solve the problem of finding the value of [tex]\( g(f(-1)) \)[/tex], follow these detailed steps:

1. Evaluate [tex]\( f(-1) \)[/tex]:
The function [tex]\( f(x) = 5x^2 + 2 \)[/tex] provides a way to calculate [tex]\( f \)[/tex] for any given [tex]\( x \)[/tex]. Substitute [tex]\( -1 \)[/tex] for [tex]\( x \)[/tex]:
[tex]\[ f(-1) = 5(-1)^2 + 2 \][/tex]
Calculate the square of [tex]\(-1\)[/tex]:
[tex]\[ (-1)^2 = 1 \][/tex]
Multiply by 5:
[tex]\[ 5 \cdot 1 = 5 \][/tex]
Add 2:
[tex]\[ 5 + 2 = 7 \][/tex]
Thus, [tex]\( f(-1) = 7 \)[/tex].

2. Evaluate [tex]\( g(7) \)[/tex]:
Now that [tex]\( f(-1) = 7 \)[/tex], we need to find [tex]\( g(7) \)[/tex] using the function [tex]\( g(x) = x^2 - 1 \)[/tex].
Substitute [tex]\( 7 \)[/tex] for [tex]\( x \)[/tex]:
[tex]\[ g(7) = 7^2 - 1 \][/tex]
Calculate the square of 7:
[tex]\[ 7^2 = 49 \][/tex]
Subtract 1:
[tex]\[ 49 - 1 = 48 \][/tex]
Therefore, [tex]\( g(7) = 48 \)[/tex].

Combining these results, the value of [tex]\( g(f(-1)) \)[/tex] is [tex]\( 48 \)[/tex].

Thus, the correct answer is:
[tex]\[ \boxed{48} \][/tex]