先化简再求值 [2x²-(x+y)(x-y)]·[(-x-y)(y-x)+2y²] 其中x=1y=2

分类: 作业答案 • 2021-12-20 12:05:58

问题描述：

答

[2x²-(x+y)(x-y)]·[(-x-y)(y-x)+2y²]= [2x²-x²+y²]·[x²-y²+2y²]=(x²+y²)²=(1+4)²=25

答

[2x²-(x+y)(x-y)]·[(-x-y)(y-x)+2y²]
=(2x^2-x^2+y^2)(x^2-y^2+2y^2)
=(x^2+y^2)(x^2+y^2)
=(x^2+y^2)^2
代入x y
=25