先化简,再求值:(xy-x^2)÷x^2-2xy+y^2/xy*x-y/x^2,其中x=2009,y=2010
问题描述：
先化简,再求值:(xy-x^2)÷x^2-2xy+y^2/xy*x-y/x^2,其中x=2009,y=2010
答
(xy-x^2)÷[(x^2-2xy+y^2)/xy]*(x-y)/x^2
=-x(x-y)*[xy/(x-y)^2]*(x-y)/x^2
=-y
y=2010
=-2010能再详细一点么，谢谢~=-x(x-y)*[xy/(x-y)^2]*(x-y)/x^2分子、分母互相约分=-y 把y=2010代入：=-20103Q