$$\frac { x } { y } = \frac { x } { y } = \frac { x } { y } = \frac { x } { y ^ { 2 } }$$
$\frac{x}{y}=\frac{x}{y^{2}}$
$\left\{\begin{matrix}x\in \mathrm{R}\text{, }&y=1\\x=0\text{, }&y\neq 0\end{matrix}\right.$
$\left\{\begin{matrix}\\y=1\text{, }&\text{unconditionally}\\y\neq 0\text{, }&x=0\end{matrix}\right.$
