Question

Find the product:
(x² − y²) × (x + 2y)

Answer 1

By horizontal method:

$$\begin{gathered} (x^2-y^2)\times (x+2y) \\ =x^2(x+2y)-y^2(x+2y) \\ =x^3+2x^{2}y-x{y}^2-2y^3 \\ i.e(x^3-2y^3)+xy(2x-y) \end{gathered}$$