化简求值【2x²-(x+y)(x-y)][(x+y-1)(x-y+1)+1-2y],其中x=-1,y=-2我思考了很久_数学解答

化简求值【2x²-(x+y)(x-y)][(x+y-1)(x-y+1)+1-2y],其中x=-1,y=-2
我思考了很久还没想出来,

人气：161 ℃　时间：2019-10-20 18:15:52

解答

【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