题抄错了,把等号改为加号来计算,即：-x-[2y-2(xy+x)的2次方+3x]+2[x+(xy-y)的2次方]的值
xy+x=-1
xy-y=-2
x+y=1
=-x-[2y-2(xy+x)^2+3x]+2[x+(xy-y)^2]
=-x-[2y-2+3x]+2[x+4]
=-x-2y-3x+2x+8
=-2x-2y+8
=-2+8
=6