令t=x+y,则dy/dx=dt/dx-1
代入原方程,化简得d(t/2)/[1+(t/2)²]=2dx
==>arctan(t/2)=2x+C (C是任意常数)
==>t
==>x+y=2tan(2x+C)
故原方程的通解是y=2tan(2x+C)-x.