令y/x=u
则y=xu
y'=u+xu'
代入得：（u-1)(u+xu')=u^2
得：xu'=u^2/(u-1)-u
xdu/dx=u/(u-1)
(u-1)du/u=dx/x
du(1-1/u)=dx/x
积分：u-ln|u|=x+c
y/x-ln|y/x|=x+c