a$.$ Find the most general real$-$valued solution to the linear system of differential equations vec$($x$)^(\text{'})=[[-4,-9],[1,-4]]$vec$($x$).$

$[[$x$\_(1)($t$)],[$x$\_(2)($t$)]]=$c$\_(1)[]+$c$\_(2)[]$

b$.$ In the phase plane, this system is best described as a

source $()/()$ unstable node

sink $()/()$ stable node

saddle

center point $()/()$ ellipses

spiral source

spiral sink

none of these