你的书写不规范
应是：[(x^2+y^2)/y-2y]/(1/y-1/x)*1/(x^2-y^2)
=[(x+y)(x-y)/y]*xy/(x-y)/[(x+y)(x-y)]
=x/(x-y)
(a+b)+a(b分之1再减a分之1)]这个意思不清楚.