(1/x+2/y+x/y^2) :y^2-x^2/xy+2/x-y=(x+y)^2/xy^2*xy/(y^2-x^2)+2/(x-y)=
=-(x+y)/(x-y)y+2/(x-y)=(y-x)/(x-y)*y=-1/y
(1/x+2/y+x/y^2) :y^2-x^2/xy+2/x-y=(x+y)^2/xy^2*xy/(y^2-x^2)+2/(x-y)=
=-(x+y)/(x-y)y+2/(x-y)=(y-x)/(x-y)*y=-1/y