方法一两端对x求导，并注意y是x的函数，有dy/dx*e^x+ye^x+1/y*dy/dx=0得dy/dx=-ye^x/(e^x+1/y)=-y^2*e^x/(1+ye^x)方法二两端求微分得e^xdy+ye^xdx+1/ydy=0得dy/dx=-ye^x/(e^x+1/y)
