A) A = (X + Y)2 – (X – Y)2 B) B = (X + Y)2 – 2(X + Y)(X – Y) + (X – Y)2 C) C = (X + Y)3 - (X – Y)3 – 2Y3

Bài 1: Rút gọn biểu thức:

a) A = (x + y)

²

– (x – y)

²

b) B = (x + y)

²

– 2(x + y)(x – y) + (x – y)

²

c) C = (x + y)

³

- (x – y)

³

– 2y

³