The function inv(A) computes the matrix inverse of A.

$\mathrm{with}\left(\mathrm{MTM}\right)\:$

$A≔\mathrm{Matrix}\left(\left[\left[1\,2\,1\right]\,\left[2\,-4\,2\right]\,\left[3\,8\,1\right]\right]\right)$

$A≔\left[\begin{array}{ccc}1& 2& 1\\ 2& \mathrm{-4}& 2\\ 3& 8& 1\end{array}\right]$

$\mathrm{inv}\left(A\right)$

$\left[\begin{array}{ccc}-\frac{5}{4}& \frac{3}{8}& \frac{1}{2}\\ \frac{1}{4}& -\frac{1}{8}& 0\\ \frac{7}{4}& -\frac{1}{8}& -\frac{1}{2}\end{array}\right]$