College

Simplify this expression.

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

A. [tex]\( 21x^2 - 9 \)[/tex]

B. [tex]\( 21x^2 - 27x^2 \)[/tex]

C. [tex]\( 21x^4 - 9 \)[/tex]

D. [tex]\( 21x^4 - 27x^2 \)[/tex]

Answer :

Sure! Let's simplify the expression [tex]\[3 x^2(7 x^2 - 9)\][/tex]

Here’s a step-by-step solution:

1. Distribute [tex]\(3 x^2\)[/tex] inside the parentheses:

[tex]\[
3 x^2 \cdot (7 x^2 - 9)
\][/tex]

2. Multiply [tex]\(3 x^2\)[/tex] with each term inside the parentheses:

- Multiply [tex]\(3 x^2\)[/tex] by [tex]\(7 x^2\)[/tex]:
[tex]\[
3 x^2 \cdot 7 x^2 = 21 x^4
\][/tex]

- Multiply [tex]\(3 x^2\)[/tex] by [tex]\(-9\)[/tex]:
[tex]\[
3 x^2 \cdot (-9) = -27 x^2
\][/tex]

3. Combine the results from the multiplication:

[tex]\[
21 x^4 - 27 x^2
\][/tex]

So, the simplified expression is:

[tex]\[
21 x^4 - 27 x^2
\][/tex]

From the given choices:
- A. [tex]\(21 x^2 - 9\)[/tex]
- B. [tex]\(21 x^2 - 27 x^2\)[/tex]
- C. [tex]\(21 x^4 - 9\)[/tex]
- D. [tex]\(21 x^4 - 27 x^2\)[/tex]

The correct option is:
[tex]\[
\boxed{21 x^4 - 27 x^2}
\][/tex]

So, the correct answer is D. [tex]\(21 x^4 - 27 x^2\)[/tex].