(x^2-xy)/(xy-y^2)-(y^2+xy)/(x^2+xy)+(x^2+y^2)/xy
=x(x-y)/(y(x-y))-y(x+y)/(x(x+y))+(x^2+y^2)/xy
=x/y-y/x+(x^2+y^2)/xy
=(x^2-y^2)/xy+(x^2+y^2)/xy
=2x^2/xy
=2x/y