Question:
Find the product:
(x4 + y4) × (x2 − y2)
Solution:
By horizontal method:
$\left(x^{4}+y^{4}\right) \times\left(x^{2}-y^{2}\right)$
$=x^{4}\left(x^{2}-y^{2}\right)+y^{4}\left(x^{2}-y^{2}\right)$
$=x^{6}-x^{4} y^{2}+y^{4} x^{2}-y^{6}$
$=\left(x^{6}-y^{6}\right)-x^{2} y^{2}\left(x^{2}-y^{2}\right)$