Question

Factorise:

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

Answer 1

$a(a+b{)}^3-3a^{2}b(a+b)=a(a+b\left)\right\{(a+b{)}^2-3ab\}=a(a+b)\{a^2+b^2+2ab-3ab\}=a(a+b)(a^2-ab+b^2)$