College

Which is the product of [tex]\left(1+4x+3x^2\right)\left(2-7x-9x^2\right)[/tex]?

A. [tex]2 - 28x^2 - 27x^4[/tex]

B. [tex]2 + x - 31x^2 - 57x^3 - 27x^4[/tex]

C. [tex]2 - 35x - 3x^2 - 57x^3 - 27x^4[/tex]

D. [tex]2 - 7x - 3x^2 - 21x^3 - 27x^4[/tex]

E. [tex]2 + 15x + 32x^2 + 57x^3 + 27x^4[/tex]

Answer :

To find the product of the polynomials [tex]\((1 + 4x + 3x^2)\)[/tex] and [tex]\((2 - 7x - 9x^2)\)[/tex], we'll follow the method of polynomial multiplication. Here's a step-by-step solution:

1. Distribute each term in the first polynomial by every term in the second polynomial. This is like applying the distributive property multiple times.

2. Multiply terms systematically:

- Start with the constant term in the first polynomial:
[tex]\[
1 \times 2 = 2
\][/tex]
[tex]\[
1 \times (-7x) = -7x
\][/tex]
[tex]\[
1 \times (-9x^2) = -9x^2
\][/tex]

- Next, the [tex]\(4x\)[/tex] term in the first polynomial:
[tex]\[
4x \times 2 = 8x
\][/tex]
[tex]\[
4x \times (-7x) = -28x^2
\][/tex]
[tex]\[
4x \times (-9x^2) = -36x^3
\][/tex]

- Lastly, the [tex]\(3x^2\)[/tex] term in the first polynomial:
[tex]\[
3x^2 \times 2 = 6x^2
\][/tex]
[tex]\[
3x^2 \times (-7x) = -21x^3
\][/tex]
[tex]\[
3x^2 \times (-9x^2) = -27x^4
\][/tex]

3. Combine like terms:

- The constant term: [tex]\(2\)[/tex]

- The [tex]\(x\)[/tex] terms: [tex]\(-7x + 8x = x\)[/tex]

- The [tex]\(x^2\)[/tex] terms: [tex]\(-9x^2 - 28x^2 + 6x^2 = -31x^2\)[/tex]

- The [tex]\(x^3\)[/tex] terms: [tex]\(-36x^3 - 21x^3 = -57x^3\)[/tex]

- The highest degree term: [tex]\(-27x^4\)[/tex]

4. Form the final expression by assembling all the combined terms:

[tex]\[
2 + x - 31x^2 - 57x^3 - 27x^4
\][/tex]

Therefore, the product of the polynomials [tex]\((1 + 4x + 3x^2)\)[/tex] and [tex]\((2 - 7x - 9x^2)\)[/tex] is:

[tex]\[ 2 + x - 31x^2 - 57x^3 - 27x^4 \][/tex]

The correct answer is option B: [tex]\(2 + x - 31x^2 - 57x^3 - 27x^4\)[/tex].