Question

化简求值 【2x²-(x+y)(x-y)][(x+y-1)(x-y+1)+1-2y],其中x=-1，y=-2

对不起我还有题不会做，麻烦帮帮忙

Answer 1

直接拆了不行吗，本来就要拆的啊……
原式=[2x^2-x^2+y^2][x^2-(y-1)^2+1-2y]
=[x^2+y^2][x^2-y^2]
=x^4-y^4
代入即可……
楼上的前半段化简错了，也不检查一下……

Answer 2

[2x²-(x+y)(x-y)][(x+y-1)(x-y+1)+1-2y]
=(2x²-x²+y²)[x²-(y-1)²+1-2y]
=(x²-y²)(x²-y²+2y-1+1-2y)
=(x²-y²)²
=(1-4)²
=9