\begin{align}
	 \left(\mathbf{M}+v^2\,\Delta t^{2} \,\mathbf{A}\right)\,\mathbf{\hat{u}}_{t_{k+1}} = \Delta t^{2}\,\mathbf{b}(t_{k+1}) + 2\, \mathbf{M}\,\mathbf{\hat{u}}_{t_{k}}-\mathbf{M}\,\mathbf{\hat{u}}_{t_{k-1}},
\end{align}
