Find the general solution to the linear system $\frac{d \mathbf{u}}{d t}=A \mathbf{u}$ for the following incomplete coefficient matrices:
(a) $\left(\begin{array}{ll}2 & 1 \\ 0 & 2\end{array}\right)$,
(b) $\left(\begin{array}{ll}2 & -1 \\ 9 & -4\end{array}\right)$,
(c) $\left(\begin{array}{rr}-1 & -1 \\ 4 & -5\end{array}\right)$.
(d) $\left(\begin{array}{rrr}4 & -1 & -3 \\ -2 & 1 & 2 \\ 5 & -1 & -4\end{array}\right)$,
(e) $\left(\begin{array}{rrr}-3 & 1 & 0 \\ 1 & -3 & -1 \\ 0 & 1 & -3\end{array}\right)$
(f) $\left(\begin{array}{rrrr}3 & 1 & 1 & 1 \\ 0 & -1 & 0 & 1 \\ 0 & 0 & 3 & 1 \\ 0 & 0 & 0 & -1\end{array}\right)$,
(g) $\left(\begin{array}{rrrr}0 & 1 & 1 & 0 \\ -1 & 0 & 0 & 1 \\ 0 & 0 & 0 & 1 \\ 0 & 0 & -1 & 0\end{array}\right)$.