y=1+xe^yy'=e^y+xe^y*y'y'(1-xe^y)=e^yy'=e^y/(1-xe^y)y''=[e^y*y'(1-xe^y)-e^y(-e^y-xe^y*y')]/(1-xe^y)^2=[e^y*y'(1-xe^y)+e^y(e^y+xe^y*y')]/(1-xe^y)^2=e^y(y'+e^y)/(1-xe^y)^2,代入y'即可得到二阶导数。
