$$\frac { d y } { d x } + 3 x ^ { 2 } y = 9 x ^ { 2 }$$
$\left\{\begin{matrix}x=0\text{, }&y\neq 3\\x\in \mathrm{R}\text{, }&y=3\end{matrix}\right.$
$\left\{\begin{matrix}y=3\text{, }&x\neq 0\\y\in \mathrm{R}\text{, }&x=0\end{matrix}\right.$
