High School

What is the product?

[tex]\[
(7x^2)(2x^3 + 5)(x^2 - 4x - 9)
\][/tex]

A. [tex]\(14x^5 - x^4 - 46x^3 - 58x^2 - 20x - 45\)[/tex]

B. [tex]\(14x^6 - 56x^5 - 91x^4 - 140x^3 - 315x^2\)[/tex]

C. [tex]\(14x^7 - 56x^6 - 126x^5 + 35x^4 - 140x^3 - 315x^2\)[/tex]

D. [tex]\(14x^{12} - 182x^6 + 35x^4 - 455x^2\)[/tex]

Answer :

Certainly! Let's find the product of the polynomials step-by-step:

We have three expressions:

1. [tex]\( 7x^2 \)[/tex]
2. [tex]\( 2x^3 + 5 \)[/tex]
3. [tex]\( x^2 - 4x - 9 \)[/tex]

Our goal is to multiply these expressions together.

### Step 1: Multiply the first two expressions

First, we'll multiply the expressions [tex]\( 7x^2 \)[/tex] and [tex]\( 2x^3 + 5 \)[/tex]:

[tex]\[
7x^2 \times (2x^3 + 5) = 7x^2 \cdot 2x^3 + 7x^2 \cdot 5
\][/tex]

Calculating each term:

- [tex]\( 7x^2 \cdot 2x^3 = 14x^5 \)[/tex]
- [tex]\( 7x^2 \cdot 5 = 35x^2 \)[/tex]

So, the product of the first two expressions is:

[tex]\[
14x^5 + 35x^2
\][/tex]

### Step 2: Multiply the result by the third expression

Now, we take the result from the first step and multiply it by the third expression [tex]\( x^2 - 4x - 9 \)[/tex]:

[tex]\[
(14x^5 + 35x^2) \times (x^2 - 4x - 9)
\][/tex]

We'll distribute each term in [tex]\( 14x^5 + 35x^2 \)[/tex] across each term in [tex]\( x^2 - 4x - 9 \)[/tex].

Expanding:

- [tex]\( 14x^5 \times x^2 = 14x^7 \)[/tex]
- [tex]\( 14x^5 \times (-4x) = -56x^6 \)[/tex]
- [tex]\( 14x^5 \times (-9) = -126x^5 \)[/tex]

Now with [tex]\( 35x^2 \)[/tex]:

- [tex]\( 35x^2 \times x^2 = 35x^4 \)[/tex]
- [tex]\( 35x^2 \times (-4x) = -140x^3 \)[/tex]
- [tex]\( 35x^2 \times (-9) = -315x^2 \)[/tex]

### Step 3: Combine all terms

Now we combine all these terms:

[tex]\[
14x^7 - 56x^6 - 126x^5 + 35x^4 - 140x^3 - 315x^2
\][/tex]

This is our final expanded polynomial after multiplying all three expressions together. Each term in the resulting polynomial corresponds to a combined and simplified multiplication of terms from the original expressions.