先化简后求值(xy-x^2)÷(x^2-2xy+y^2)/(xy)*(x-y)/(x^2) x=-2005 y=-2

问题描述:

先化简后求值(xy-x^2)÷(x^2-2xy+y^2)/(xy)*(x-y)/(x^2) x=-2005 y=-2

原式=-x(x-y)*xy/(x-y)²*(x-y)/x²
=-x²y/(x-y)*(x-y)/x²
=-y
=-(-2)
=2怎么得的-y?约分采纳吧