I have been trying to find the inverse matrix of the following matrix (mod 19)
$\displaystyle A = \begin{bmatrix} 1 & 14 & 9 \\ 7 & 15 & 8 \\ 2 & 13 & 4\end{bmatrix} mod 19. $.
I used gauss-jordan elimination method (i.e. augment A with identity matrix, and reduce the left matrix to an identity matrix) and its very tedious. Everytime i change an element, another element of the same row gets affected then i have to go back and redo all over.
Is there an efficent way to do this? Thanks in advance for your help.