Question

化简求值:[2x的平方-(x+y)(x-y)][(-x-y)(y-x)+2y的平方],其中x=1,y=2

Answer 1

[2x的平方-(x+y)(x-y)][(-x-y)(y-x)+2y的平方]
=[2x²-(x²-y²)][(x+y)(x-y)+2y²]
=(2x²-x²+y²)(x²-y²+2y²)
=(x²+y²)/(x²+y²)
=1

Answer 2

　　[2x²-(x+y)(x-y)][(-x-y)(y-x)+2y²]
　　=[2x²-(x²-y²)][(x+y)(x-y)+2y²]
　　=(2x²-x²+y²)(x²-y²+2y²)
　　=(x²+y²)(x²+y²)
　　=(x²+y²)²
　　∵x=1,y=2
　　∴原式 =（1+4）²
=25