College

Multiply the following expressions:

\[
\begin{array}{r}
x^2 + 4x + 2 \\
\times \quad (2x^2 + 3x - 4) \\
\hline
\end{array}
\]

Choose the correct product:

A. [tex]\(3x^2 + 7x - 2\)[/tex]

B. [tex]\(2x^4 + 23x^2 - 10x - 8\)[/tex]

C. [tex]\(2x^4 + 12x^2 - 8\)[/tex]

D. [tex]\(2x^4 + 11x^3 + 12x^2 - 10x - 8\)[/tex]

Answer :

To find the product of the two polynomials [tex]\((x^2 + 4x + 2)\)[/tex] and [tex]\((2x^2 + 3x - 4)\)[/tex], we are going to multiply each term in the first polynomial by each term in the second polynomial and then combine like terms.

Here’s how you can do it step-by-step:

1. Multiply each term in the first polynomial by each term in the second polynomial:

- Multiply [tex]\( x^2 \)[/tex] by each term in the second polynomial:
- [tex]\( x^2 \times 2x^2 = 2x^4 \)[/tex]
- [tex]\( x^2 \times 3x = 3x^3 \)[/tex]
- [tex]\( x^2 \times (-4) = -4x^2 \)[/tex]

- Multiply [tex]\( 4x \)[/tex] by each term in the second polynomial:
- [tex]\( 4x \times 2x^2 = 8x^3 \)[/tex]
- [tex]\( 4x \times 3x = 12x^2 \)[/tex]
- [tex]\( 4x \times (-4) = -16x \)[/tex]

- Multiply [tex]\( 2 \)[/tex] by each term in the second polynomial:
- [tex]\( 2 \times 2x^2 = 4x^2 \)[/tex]
- [tex]\( 2 \times 3x = 6x \)[/tex]
- [tex]\( 2 \times (-4) = -8 \)[/tex]

2. Combine all these products together:

[tex]\( 2x^4 + 3x^3 - 4x^2 + 8x^3 + 12x^2 - 16x + 4x^2 + 6x - 8 \)[/tex]

3. Combine like terms:

- For [tex]\( x^4 \)[/tex], we have [tex]\( 2x^4 \)[/tex].
- For [tex]\( x^3 \)[/tex], combine [tex]\( 3x^3 + 8x^3 = 11x^3 \)[/tex].
- For [tex]\( x^2 \)[/tex], combine [tex]\(-4x^2 + 12x^2 + 4x^2 = 12x^2 \)[/tex].
- For [tex]\( x \)[/tex], combine [tex]\(-16x + 6x = -10x \)[/tex].
- The constant term is [tex]\(-8\)[/tex].

Putting it all together, the final answer is:

[tex]\[ 2x^4 + 11x^3 + 12x^2 - 10x - 8 \][/tex]

This corresponds to choice D.