t=x+ydt/dx=1+dy/dxdy/dx=dt/dx-1t^2(dt/dx -1)=1dt/dx -1=1/t^2dt/dx=1/t^2+1=(t^2+1)/t^2t^2dt/(t^2+1)=dxdt-dt/(t^2+1)=dxt-arctant =x+Cx+y-arctan(x+y)=x+Cy-arctan(x+y)-C=0