先化简,再求值:[2x的2次方-(x+y)(x-y)] [(-x-y)(-x+y)+2y的2次方],其中x=-1,y=-2
问题描述:
先化简,再求值:[2x的2次方-(x+y)(x-y)] [(-x-y)(-x+y)+2y的2次方],其中x=-1,y=-2
答
[2x的2次方-(x+y)(x-y)] [(-x-y)(-x+y)+2y的2次方]
=(2x²-x²+y²)(x²-y²+2y²(
=(x²+y²)²
当x=-1,y=-2时
原式=(1+4)²=25