Question

The factorisation of $3a^5-108a^3$ is equal to

• A. $3a^3(a+6)(a+6)$
• B. $3a^3(a-6)(a+6)$
• C. $3a^2(a-6)(a-6)$
• D. $3a^3(a-6)(a+6)$

Answer 1

The correct option is B $3a^3(a-6)(a+6)$

The given expression is $3a^5-108a^3$
Taking out $3a^3$ we get

$3a^3(a^2-36)$
= $3a^3(a^2-6^2)$
= $3a^3(a-6)(a+6)$