当x=-1,y=-2时,求代数式[2x2-(x+y)(x-y)][(-x-y)(-x+y)+2y2]的值.

问题描述:

当x=-1,y=-2时,求代数式[2x2-(x+y)(x-y)][(-x-y)(-x+y)+2y2]的值.

原式=[2x2-x2+y2][(-x)2-y2+2y2]
=(x2+y2)(x2+y2
=(x2+y22
当x=-1,y=-2时,
原式=(1+4)2=25.