两边对x求导:
y'e^x+ye^x-e^y-xy'e^y+1=0
y'(e^x-xe^y)=e^y-ye^x-1
y'=(e^y-ye^x-1)/(e^x-xe^y)
dy=(e^y-ye^x-1)/(e^x-xe^y)dx