xdy+ydy+x^2dx+ydx=0xdy+ydx+ydy+x^2dx=0d(xy)+d[(1/2)y^2]+d[(1/3)x^3]=0d[(xy)+(1/2)y^2+(1/3)x^3]=0(xy)+(1/2)y^2+(1/3)x^3=C
