y'+y/x=(y/x)^2令y/x=u,则y'=u+xu'所以u+xu'+u=u^2xdu/dx=u^2-2udu/(u^2-2u)=dx/x两边积分:∫du/[u(u-2)]=ln|x|+C左边=1/2∫(1/(u-2)-1/u)du=1/2ln|(u-2)/u|+C所以ln|(u-2)/u|=2ln|x|+C(u-2)/u=1-2/u=1-2x/y=Cx^22x/y=1-Cx^2y=2x/(1-Cx^2)