e^y-xy=e
e^y·dy/dx-(y+x·dy/dx)=0
e^y·dy/dx-y-x·dy/dx=0
(e^y-x)·dy/dx=y
dy/dx=y/(e^y-x)
dy/dx不能叫做dx分之dy,因为这是个导数符号,而不是分数!