Solve this following

If $\mathrm{A}=\left[\begin{array}{ll}1 & 1 \\ 0 & 1\end{array}\right]$, prove that $\mathrm{A}^{\mathrm{n}}=\left[\begin{array}{ll}1 & \mathrm{n} \\ 0 & 1\end{array}\right]$ for all $\mathrm{n} \in \mathrm{N}$