$$Lt=\frac{2^{y}-2^{-y}}{2^{y}+2^{-y}}$$
$\left\{\begin{matrix}L=-\frac{1-4^{y}}{t\left(4^{y}+1\right)}\text{, }&t\neq 0\\L\in \mathrm{R}\text{, }&y=0\text{ and }t=0\end{matrix}\right.$
$\left\{\begin{matrix}t=-\frac{1-4^{y}}{L\left(4^{y}+1\right)}\text{, }&L\neq 0\\t\in \mathrm{R}\text{, }&y=0\text{ and }L=0\end{matrix}\right.$