解:令y=xt,则y'=xt'+t
代入原方程,化简得 x(1+t)t'+1+t^2=0
==>x(1+t)dt+(1+t^2)dx=0
==>(1+t)dt/(1+t^2)+dx/x=0
==>∫(1+t)dt/(1+t^2)+∫dx/x=0
==>arctant+(1/2)ln(1+t^2)+ln│x│=ln│C│ (C是积分常数)
==>x√(1+t^2)*e^(arctant)=C
==>x√(1+(y/x)^2)*e^(arctan(y/x))=C
==>√(x^2+y^2)*e^(arctan(y/x))=C
故原方程的通解是√(x^2+y^2)*e^(arctan(y/x))=C