Question

$(a+b{)}^3-(a-b{)}^3$ =________

• A. $b^3+3a^{2}b$
• B. $2(b^3+3a^{2}b)$
• C. $2(a^3+3a{b}^2)$
• D. 0

Answer 1

The correct option is B

$2(b^3+3a^{2}b)$

$(a+b{)}^3-(a-b{)}^3$
$=(a^3+b^3+3a^{2}b+3a{b}^2)$-$(a^3-b^3-3a^{2}b+3a{b}^2)$
$=a^3+b^3+3a^{2}b+3a{b}^2-a^3+b^3+3a^{2}b-3a{b}^2$
$=2(b^3+3a^{2}b)$