$$y1(x)=x2$$
$\left\{\begin{matrix}x=\frac{x_{2}}{y_{1}}\text{, }&y_{1}\neq 0\\x\in \mathrm{C}\text{, }&x_{2}=0\text{ and }y_{1}=0\end{matrix}\right.$
$\left\{\begin{matrix}x=\frac{x_{2}}{y_{1}}\text{, }&y_{1}\neq 0\\x\in \mathrm{R}\text{, }&x_{2}=0\text{ and }y_{1}=0\end{matrix}\right.$
$x_{2}=xy_{1}$
