Chapter 6.5, Problem 15P

Solve the initial value problem

$\text{x}\text{'}=\left(\begin{array}{cc}-3& -9\\ 1& -3\end{array}\right)\text{x,}\text{x}\left(0\right)=\left(\begin{array}{c}4\\ 1\end{array}\right)$

by using the fundamental matrix $e^{\text{At}}$ found in problem $6$.