(w + 2t)(w^2 - 2wt + 4t^2)

Question

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

= x^3-2x^2y-xy^2+2y^3