Question

[270741257]

Rút gọn biểu thức:

a) (x + y)² + (x - y)²;

b) 2(x - y)(x + y) +(x - y)² + (x + y)²;

c) (x - y + z)² + (z - y)² + 2(x - y + z)(y - z).

Answer 1

[Diệu Anh]

a) (x+y)² + (x-y)²

= x² + 2xy + y² + x²  - 2xy+ y²

= 2x² + 2y²

b) 2(x-y)(x+y) + (x-y)² + (x+y)²

= (x+y + x-y)²

= 4x²

c) (x-y+z)² +  (z-y)² +2 (x-y+z) (y-z)

= (x-y+z)² + 2(x-y+z)(y-z) + (y-z)²

= (x-y+z+ y-z)²

=x²