d) (x – y)(x^2 – 2xy + y^2).
Giải thích
d) (x – y)(x2 – 2xy + y2)
= x . x2 – x . 2xy + x . y2 – y . x2 – y . (– 2xy) – y . y2
= x3 – 2x2y + xy2 – x2y + 2xy2 – y3
= x3 – (2x2y + x2y) + (xy2 + 2xy2) – y3
= x3 – 3x2y + 3xy2 – y3.
d) (x – y)(x2 – 2xy + y2)
= x . x2 – x . 2xy + x . y2 – y . x2 – y . (– 2xy) – y . y2
= x3 – 2x2y + xy2 – x2y + 2xy2 – y3
= x3 – (2x2y + x2y) + (xy2 + 2xy2) – y3
= x3 – 3x2y + 3xy2 – y3.