High School

[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 + 12x^2 - 7x - 28[/tex]
B. [tex](f \cdot g)(x) = 3x^3 - 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 solve for [tex]\((f \cdot g)(x)\)[/tex] given the functions [tex]\(f(x) = x + 4\)[/tex] and [tex]\(g(x) = 3x^2 - 7\)[/tex], we need to find the product of [tex]\(f(x)\)[/tex] and [tex]\(g(x)\)[/tex].

The product [tex]\((f \cdot g)(x)\)[/tex] is calculated as follows:

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

Substitute the given functions into the equation:

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

Next, expand the expression by using the distributive property (i.e., multiply each term in the first polynomial by each term in the second polynomial):

1. Multiply [tex]\(x\)[/tex] by [tex]\(3x^2\)[/tex]:
[tex]\[ x \cdot 3x^2 = 3x^3 \][/tex]

2. Multiply [tex]\(x\)[/tex] by [tex]\(-7\)[/tex]:
[tex]\[ x \cdot (-7) = -7x \][/tex]

3. Multiply [tex]\(4\)[/tex] by [tex]\(3x^2\)[/tex]:
[tex]\[ 4 \cdot 3x^2 = 12x^2 \][/tex]

4. Multiply [tex]\(4\)[/tex] by [tex]\(-7\)[/tex]:
[tex]\[ 4 \cdot (-7) = -28 \][/tex]

Now, combine all these results:

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

Rearrange the terms in descending order of powers of [tex]\(x\)[/tex]:

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

Therefore, the correct answer is:

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