Question

Simplify 3x ^3 + 3 (3x^ 3 − 7b^ 5 ).

A. 12x^3 − 7b^5

B. 12x^3 − 21b^5

C. 3x^3 − 30x^3 b^5

D. 12x^6 − 21b^5

Answer 1

From your selections of answers, It's B: 12 x^3 - 21 b^5, but it's not completely simplified.

Explanation:

Simplify the following:

3 (3 x^3 - 7 b^5) + 3 x^3

3 (3 x^3 - 7 b^5) = 9 x^3 - 21 b^5:

3 x^3 + (9 x^3 - 21 b^5)

Grouping like terms, 9 x^3 + 3 x^3 - 21 b^5 = (3 x^3 + 9 x^3) - 21 b^5:

(3 x^3 + 9 x^3) - 21 b^5

3 x^3 + 9 x^3 = 12 x^3:

12 x^3 - 21 b^5

Factor 3 out of 12 x^3 - 21 b^5:

Answer: (3 (4 x^3 - 7 b^5)) = 12 x^3 - 21 b^5