Q. If $A=\begin{bmatrix}1 & 1 & 1 & 1 \\ 1 & 1 & 1 & 1 \\ 1 & 1 & 1 & 1 \\ 1 & 1 & 1 & 1\end{bmatrix}$ then $A^{4}=$

Solution:

since $A$ is $4 \times 4$ matrix
then $A^{n}=4^{n-1} A$
$\therefore A^{4}=4^{4-1} A=4^{3} A=64\, A$