High School

What is the product?

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

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

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

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

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

Answer :

We begin with the expression

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

Step 1. Multiply the first two factors

Multiply [tex]$7x^2$[/tex] by each term in [tex]$(2x^3+5)$[/tex]:

[tex]$$
7x^2 \cdot 2x^3 = 14x^5,
$$[/tex]

[tex]$$
7x^2 \cdot 5 = 35x^2.
$$[/tex]

Thus, the product of the first two factors is

[tex]$$
14x^5 + 35x^2.
$$[/tex]

Step 2. Multiply the result by the third factor

We now multiply

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

Distribute each term in [tex]$14x^5 + 35x^2$[/tex] across every term in [tex]$x^2 - 4x - 9$[/tex].

Multiplying [tex]$14x^5$[/tex] by each term:

[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]

Multiplying [tex]$35x^2$[/tex] by each term:

[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]

Step 3. Combine all terms

Gathering all the results, we have

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

This is the final product.

Thus, the product is

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