Simplify:
(x + y) (x2 -xy + y2 )
(x + y) (x2 -xy + y2 )
= x(x2 - xy + y2 ) + y(x2 - xy + y2 )
= ( x X x2 ) - (x X xy) + ( x X y2 ) + (y x X2 ) - ( y X xy) + (y x y2 )
= x3 - x2y + xy2 + yx2 - xy2 + y3
= x3 + (- x2y + x2y )+ (xy2 - xy2 )+ y3
= x3 + 0 + 0 + y3 = x3 + y3
Consider the special case of Identity (IV) with a = b, what do you get? Is it related to Identity (1)?
Consider, the special case of Identity (IV) with a = –c and b = –c. What do you get? Is it related to Identity (II)?