Question

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

Answer 1

【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)(x²-y²)

=X^4-Y^4

把x=-1,y=-2代人上式得：

(-1)^4-(-2)^4

=1-16

=-15