方程两边求关x的导数ddx(xy)＝(y+xdydx)；     ddxex+y＝ex+y(1+dydx)；所以有  （y+xdydx）=ex+y（1+dydx）解得   dydx＝ex+y−yx−ex+y＝xy−yx−xy＝y(x−1)x(1−y...