dx/dy=(2x-y)/(x+y)

u=y/x y'=u+xu'
u+xu'=(2-u)/(1+u)
xu'=(2-u)/(1+u)-u=(2-u-u-u^2)/(1+u)
(1+u)/(-u^2-2u+2) du=dx/x
(-1/2)log│-u^2-2u+2│=log(c│x│)
│-u^2-2u+2│=e^( log(c│x│)^(-2) )=c│x│^(-2)
-u^2-2u+2=C/x^2
-(y^2/x^2)-2(y/x)+2=C/x^2
-y^2-2xy+2x^2=C
2x^2-2xy-y^2=C