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