dx/dy=x+ydx-(x+y)dy=0,(x+y)dy/dx=1∵M=1,N=-(x+y),∂M/∂y=0,∂N/∂x=-1[∂M/∂y-∂N/∂x]/M=+1∴I=e^∫(-1)dy=e^(-y)d[e^(-y)*(x+y)]=e^(-y)dye^(-y)*(x+y)=-e^(-y)+c∴...