为你提供精确解答
[(x-2y)²-(x+2y)(x-2y)∕(-4y)
=[(x^2+4 y^2-4 xy)-(x^2-4 y^2)]/(-4y)
=[8 y^2-4 xy]/(-4y)
=-2y+x
代入x=-1,y=2
得：-2y+x=-4-1=-5