b) (x + y)(x^2 – xy + y^2);
Giải thích
b) (x + y)(x2 – xy + y2)
= x . x2 – x . xy + x . y2 + y . x2 – y . xy + y . y2
= x3 – x2y + xy2 + x2y – xy2 + y3
= x3 + (x2y – x2y) + (xy2 – xy2) + y3
= x3 + y3.
b) (x + y)(x2 – xy + y2)
= x . x2 – x . xy + x . y2 + y . x2 – y . xy + y . y2
= x3 – x2y + xy2 + x2y – xy2 + y3
= x3 + (x2y – x2y) + (xy2 – xy2) + y3
= x3 + y3.