PROBLEM: Determine whether the system
\dot{x}= Ax + Bu=\left[\begin{matrix} -2 & -1 & -3 \\ 0 & -2 & 1 \\ -7 & -8 & -9 \end{matrix} \right] x+\left[\begin{matrix} 2 \\ 1 \\ 2 \end{matrix} \right] uy =Cx=\left[\begin{matrix} 4 & 6 & 8\end{matrix} \right] x
is observable.