High School

Given [tex]f(x) = -4x + 7[/tex] and [tex]g(x) = x^3[/tex], choose the expression for [tex](f \circ g)(x)[/tex].

A. [tex]-4x^3 + 7x^3[/tex]
B. [tex](-4x + 7)^3[/tex]
C. [tex]-4x^3 + 7[/tex]
D. [tex]-12x^3 + 21[/tex]

Answer :

Sure! Let's work through finding [tex]\((f^{\circ} g)(x)\)[/tex] step by step. The notation [tex]\(f^{\circ} g\)[/tex] represents the composition of the functions [tex]\(f(x)\)[/tex] and [tex]\(g(x)\)[/tex], which means you substitute [tex]\(g(x)\)[/tex] into [tex]\(f(x)\)[/tex].

Given:
- [tex]\(f(x) = -4x + 7\)[/tex]
- [tex]\(g(x) = x^3\)[/tex]

We need to find [tex]\(f(g(x))\)[/tex], which means we will input [tex]\(g(x)\)[/tex] into [tex]\(f(x)\)[/tex]:

1. Start with the expression for [tex]\(g(x)\)[/tex]:
[tex]\[
g(x) = x^3
\][/tex]

2. Substitute [tex]\(g(x)\)[/tex] into [tex]\(f(x)\)[/tex]:
[tex]\[
f(g(x)) = f(x^3)
\][/tex]

3. Replace every [tex]\(x\)[/tex] in [tex]\(f(x) = -4x + 7\)[/tex] with [tex]\(x^3\)[/tex]:
[tex]\[
f(x^3) = -4(x^3) + 7
\][/tex]

Thus, the expression for [tex]\((f^{\circ} g)(x)\)[/tex] is:
[tex]\[
-4x^3 + 7
\][/tex]

So, the correct choice is:
[tex]\[
-4x^3 + 7
\][/tex]