High School

What is the product of the following expression?

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

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 :

To find the product of the expression [tex]\((7x^2)(2x^3 + 5)(x^2 - 4x - 9)\)[/tex], we will follow these steps:

1. Expand the Expression:
We need to multiply the three expressions together. Start by multiplying any two expressions first and then multiply the result by the third expression.

2. Multiply the First Two Terms:
- Multiply [tex]\(7x^2\)[/tex] with each term in the expression [tex]\((2x^3 + 5)\)[/tex].

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

- This gives us:

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

3. Multiply the Result with the Third Term:
- Now multiply [tex]\((14x^5 + 35x^2)\)[/tex] with [tex]\((x^2 - 4x - 9)\)[/tex]:

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

- Distribute each term in the first expression across all terms in the second expression.

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

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

5. Combine Like Terms:
Since all terms are already unique in degrees, no terms to combine further.

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

This is the expanded form of the given product expression.