High School

What is the product?

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

To solve for the product of the expression [tex]\((7x^2)(2x^3 + 5)(x^2 - 4x - 9)\)[/tex], we will break it down into manageable steps:

1. Distribute the First Two Factors:

We start by distributing the first two terms: [tex]\((7x^2)(2x^3 + 5)\)[/tex].

- First, distribute [tex]\(7x^2\)[/tex] to [tex]\(2x^3\)[/tex]:
[tex]\[
7x^2 \cdot 2x^3 = 14x^5
\][/tex]

- Next, distribute [tex]\(7x^2\)[/tex] to [tex]\(5\)[/tex]:
[tex]\[
7x^2 \cdot 5 = 35x^2
\][/tex]

This means our intermediate expression is:
[tex]\[
14x^5 + 35x^2
\][/tex]

2. Distribute the Result with the Third Factor:

Next, we need to multiply the result by the third factor: [tex]\((x^2 - 4x - 9)\)[/tex].

Let's distribute each term in the binomial [tex]\((14x^5 + 35x^2)\)[/tex] through [tex]\((x^2 - 4x - 9)\)[/tex]:

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

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

3. Combine All the Terms:

Now, combine all the like terms from these results:
[tex]\[
14x^7 - 56x^6 - 126x^5 + 35x^4 - 140x^3 - 315x^2
\][/tex]

That's the expanded polynomial representing the product of the original expression. The coefficients and the degrees of the terms match perfectly with what we found, confirming our solution.