Exercise 104

Suppose $a, b, c$ are nonzero numbers. Let $M=\left[ \begin{smallmatrix} a & 0 \\ 0 & b \end{smallmatrix}\right]$, $N=\left[ \begin{smallmatrix} a & 0 & 0 \\ 0 & b & 0 \\ 0 & 0 & c \end{smallmatrix}\right]$.

1. Compute $M^{-1}$.
2. Compute $N^{-1}$.