Assuming general initial conditions, express the system model in

a. Configuration form.

b. Standard, second-order matrix form.

\(\left\{\begin{array}{l}\frac{1}{2} \ddot{x}_{1}+\dot{x}_{1}+\frac{1}{3}\left(x_{1}-x_{2}\right)=0 \\ \ddot{x}_{2}+\frac{1}{2} \dot{x}_{2}-\frac{1}{3}\left(x_{1}-x_{2}\right)=e^{-2 t / 3}\end{array}\right.\)