y^2dx-(1-2xy)dy=0y^2dx+2xydy=dyy^2dx+2xdy^2=dyd(xy^2)=dy通解xy^2=y+C
不是y²dx-(1-2xy)dy=y²dx+2xydy-dy=y²dx+xdy²-dy=d(xy²)-dy=0所以xy²-y=Cx=1/y+C/y²
