Question

Choose the correct simplification of 9x2(4x + 2x2 − 1). 18x4 + 36x3 − 9x2 18x4 − 36x3 + 9x2 36x4 + 18x3 − 9x2 36x4 − 13x3 + 9x2

Answer 1

Distribute 9x^2 to all terms in parentheses:

$9x^{2} \times 4x = 36x^{3}$
$9x^{2} \times 2x^{2} = 18x^{4}$
$9x^{2} \times -1 = -9x^{2}$

$18x^4 + 36x^3 - 9x^2$

The answer is 18x^4 + 36x^3 − 9x^2.

Answer 2

You have 3 terms inside the parentheses.  One by one, you must mult. each of these terms by 9x^2.

9x^2(4x + 2x^2 - 1) = 36x^3 + 18x^4 - 9x^2

Be sure to use " ^ " for exponentiation:  x^2, not x2.