设可微函数 $f(x,y)$ 满足方程 $(1+y)f(x,y)+xy\frac{\partial f}{\partial x}+y\frac{\partial f}{\partial y}=0$, 求 $f(x,y)$.
设可微函数 $f(x,y)$ 满足方程 $(1+y)f(x,y)+xy\frac{\partial f}{\partial x}+y\frac{\partial f}{\partial y}=0$, 求 $f(x,y)$.
设可微函数 $f(x,y)$ 满足方程 $(1+y)f(x,y)+xy\frac{\partial f}{\partial x}+y\frac{\partial f}{\partial y}=0$, 求 $f(x,y)$.