8. Let $x' = Ax$, where
$A = \begin{pmatrix} 2 & 6 \ 7 & 1 \end{pmatrix}$
(a) (7 points) Find the general solution for this system.
(b) (3 points) Find the type and stability of the equilibrium at the origin (stable/unstable, node/saddle/spiral).
(c) (5 points) Sketch the phase portrait of the system in $x_1$-$x_2$ plane.