Find the free response of the differential equation: \[ \frac{d^{3} y}{d t^{3}}+4 \frac{d^{2} y}{d t^{2}}+6 \frac{d y}{d t}+4 y=u \] with initial conditions: \( y(t=0)=1, \dot{y}(t=0)=0, \ddot{y}(t=0)