High School

Simplify [tex]\((x+6)(2x^2+x-7)\)[/tex].

A) [tex]\(14x^3 + 31x^2 + 8x - 5\)[/tex]

B) [tex]\(6x^3 - 15x^2 - 18x + 48\)[/tex]

C) [tex]\(42x^3 - 19x^2 - 56x - 15\)[/tex]

D) [tex]\(2x^3 + 13x^2 - x - 42\)[/tex]

Answer :

To properly expand the expression [tex]\((x + 6)(2x^2 + x - 7)\)[/tex], we'll distribute each term in the first polynomial with each term in the second polynomial. Let’s go step-by-step:

1. Distribute [tex]\(x\)[/tex] to each term in [tex]\((2x^2 + x - 7)\)[/tex]:

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

Adding these, we get:
[tex]\[
2x^3 + x^2 - 7x
\][/tex]

2. Distribute [tex]\(6\)[/tex] to each term in [tex]\((2x^2 + x - 7)\)[/tex]:

- [tex]\(6 \cdot 2x^2 = 12x^2\)[/tex]
- [tex]\(6 \cdot x = 6x\)[/tex]
- [tex]\(6 \cdot (-7) = -42\)[/tex]

Adding these, we get:
[tex]\[
12x^2 + 6x - 42
\][/tex]

3. Combine all the terms from the two distributions:

[tex]\[
(2x^3 + x^2 - 7x) + (12x^2 + 6x - 42)
\][/tex]

4. Combine like terms:

- For [tex]\(x^3\)[/tex] terms: [tex]\(2x^3\)[/tex]
- For [tex]\(x^2\)[/tex] terms: [tex]\(x^2 + 12x^2 = 13x^2\)[/tex]
- For [tex]\(x\)[/tex] terms: [tex]\(-7x + 6x = -x\)[/tex]
- Constant term: [tex]\(-42\)[/tex]

Resulting in:
[tex]\[
2x^3 + 13x^2 - x - 42
\][/tex]

The expanded expression matches option D: [tex]\(2x^3 + 13x^2 - x - 42\)[/tex]. So, the correct answer is D.