College

Given the functions:

[tex]
\begin{array}{l}
f(x)=x+4 \\
g(x)=3x^2-7
\end{array}
[/tex]

Find [tex](f \cdot g)(x)[/tex].

A. [tex](f \cdot g)(x) = 3x^3 - 28[/tex]

B. [tex](f \cdot g)(x) = 3x^3 + 12x^2 + 7x + 28[/tex]

C. [tex](f \cdot g)(x) = 3x^3 + 12x^2 - 7x - 28[/tex]

D. [tex](f \cdot g)(x) = 3x^3 + 28[/tex]

Answer :

To find [tex]\((f \cdot g)(x)\)[/tex], we need to multiply the functions [tex]\(f(x)\)[/tex] and [tex]\(g(x)\)[/tex] together. Let's start by writing down these functions:

- [tex]\(f(x) = x + 4\)[/tex]
- [tex]\(g(x) = 3x^2 - 7\)[/tex]

The product [tex]\((f \cdot g)(x)\)[/tex] is given by:

[tex]\[
(f \cdot g)(x) = f(x) \times g(x)
\][/tex]

Substituting the expressions for [tex]\(f(x)\)[/tex] and [tex]\(g(x)\)[/tex], we get:

[tex]\[
(f \cdot g)(x) = (x + 4)(3x^2 - 7)
\][/tex]

Now, let's expand this expression by distributing each term in [tex]\(x + 4\)[/tex] with each term in [tex]\(3x^2 - 7\)[/tex].

1. Multiply the [tex]\(x\)[/tex] in [tex]\(x + 4\)[/tex] with each term in [tex]\(3x^2 - 7\)[/tex]:

[tex]\[
x \times 3x^2 = 3x^3
\][/tex]
[tex]\[
x \times (-7) = -7x
\][/tex]

2. Multiply the [tex]\(4\)[/tex] in [tex]\(x + 4\)[/tex] with each term in [tex]\(3x^2 - 7\)[/tex]:

[tex]\[
4 \times 3x^2 = 12x^2
\][/tex]
[tex]\[
4 \times (-7) = -28
\][/tex]

Now, combine all these products:

[tex]\[
3x^3 + 12x^2 - 7x - 28
\][/tex]

Therefore, the expression for [tex]\((f \cdot g)(x)\)[/tex] is:

[tex]\[
3x^3 + 12x^2 - 7x - 28
\][/tex]

So, the correct choice is C: [tex]\( \boxed{3x^3 + 12x^2 - 7x - 28} \)[/tex].