- 化简求值(利用公式)(1)(x+y)²(x
- (1)(x+y)²(x-y)²-(x-y)(x+y)(x²+y²)
(2)(x+y-2)(x-y+2)
(3)(x-y)(x+y)+(x-y)+(x+y)
- (1)
(x+y)²(x-y)²-(x-y)(x+y)(x²+y²)
=(x+y)(x-y)(x+y)(x-y)-(x-y)(x+y)(x²+y²)
=(x²-y²)(x²-y²)-(x²-y²)(x²+y²)
=(x²-y²)[(x²-y²)-(x²+y²)]
=-2y²(x²-y²)
(2)
(x+y-2)(x-y+2)
=[x+(y-2),x-(y-2)]
=x²-(y-2)²
=x²-y²+4y-4
(3)
(x-y)(x+y)+(x-y)+(x+y)
=x²-y²+2x