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If [tex]\( h(x)=x-7 \)[/tex] and [tex]\( g(x)=x^2 \)[/tex], which expression is equivalent to [tex]\( (g \circ h)(5) \)[/tex]?

A. [tex]\((5-7)^2\)[/tex]
B. [tex]\(5^2 - 7\)[/tex]
C. [tex]\(5^2 (5-7)\)[/tex]
D. [tex]\((5-7) x^2\)[/tex]


Sagot :

To solve the given problem, we need to find the value of the composite function [tex]\((g \circ h)(5)\)[/tex], given the functions [tex]\(h(x)\)[/tex] and [tex]\(g(x)\)[/tex].

1. We start with the inner function [tex]\(h(x)\)[/tex] which is [tex]\(h(x) = x - 7\)[/tex].
- Evaluate [tex]\(h(5)\)[/tex]:
[tex]\[ h(5) = 5 - 7 = -2 \][/tex]

2. Next, we use the result from [tex]\(h(5)\)[/tex] to find [tex]\(g(h(5))\)[/tex]. The outer function [tex]\(g(x)\)[/tex] is [tex]\(g(x) = x^2\)[/tex].
- Substitute the value obtained from [tex]\(h(5)\)[/tex] into [tex]\(g(x)\)[/tex]:
[tex]\[ g(-2) = (-2)^2 = 4 \][/tex]

Thus, [tex]\((g \circ h)(5) = g(h(5)) = g(-2) = 4\)[/tex].

Now, we check which of the given expressions is equivalent to this computation:

1. [tex]\((5-7)^2\)[/tex]:
[tex]\[ (5 - 7)^2 = (-2)^2 = 4 \][/tex]

2. [tex]\((5)^2 - 7\)[/tex]:
[tex]\[ 5^2 - 7 = 25 - 7 = 18 \][/tex]

3. [tex]\((5)^2(5-7)\)[/tex]:
[tex]\[ 5^2 (5 - 7) = 25 \times (-2) = -50 \][/tex]

4. [tex]\((5-7) x^2\)[/tex]:
[tex]\[ (5 - 7) x^2 = -2 x^2 \text{ (This expression has an x variable and does not match our requirement.)} \][/tex]

Since [tex]\( (g \circ h)(5) = 4 \)[/tex], the correct equivalent expression is:

[tex]\[ (5 - 7)^2 \][/tex]

Thus, the correct expression is [tex]\((5-7)^2\)[/tex].