An explicit decomposition formula of a matrix in $GL_{2}\left(\mathbb{Z}\right)$

Abstract

Given $A:=\left(\begin{smallmatrix}1&1\\0&1\end{smallmatrix}\right)$, $B:=\left(\begin{smallmatrix}1&0\\1&1\end{smallmatrix}\right)$ and $C:=\left(\begin{smallmatrix}1&0\\0&-1\end{smallmatrix}\right)$ three elements of $GL_{2}\left(\mathbb{Z}\right)$, we propose an explicit formula that provides the decomposition of any $M\in GL_{2}\left(\mathbb{Z}\right)$ in $\langle A,B,C\rangle$.