Proofs Involving Real Numbers question

Question

my question is about Proofs Involving Real Numbers which is :

Let $x,y ∈ \Bbb R$, prove that if $x<0 $, then $x^3-x^2y \le x^2y-xy^2$

Answer 1

Write $$x^2(x-y)\le xy(x-y)$$ and then? we get $$-x(x-y)^2\geq 0$$ since we have $-x>0$