a. Plot the response \(x\) by using the step and initial commands, showing the step response, the initial response and the total response in one figure. Verify the steady-state value of \(x\).
b. Plot the response \(x\) by using the lsim command.

\(u(t)\) denotes the unit step.
\(9 \ddot{x}+12 \dot{x}+4 x=0.6 u(t), x(0)=\frac{2}{3}, \dot{x}(0)=0\)