Question

factorize
$x(x {}^{3} - y {}^{3} ) + 3xy(x - y)$

Answer 1

$x(x^3-y^3)+3xy(x-y)=x(x-y)(x^2+xy+y^2)+3xy(x-y)\\\\=x(x-y)(x^2+xy+y^2+3y)$

$Use:a^3-b^3=(a-b)(a^2+ab+b^2)$

Answer 2

x(x - y)(x² + xy + y²) + 3xy(x - y) ← pull the common factors from both terms
x(x - y)(x² + xy + 3y + y²) ← the remaining parts are combined
x(x - y)(x² + y(x + 3) + y²)

I just got wild with this one...