If a particle moves in a straight line such that the distance travelled in time t is given by

$s=t^{3}-6 t^{2}+9 t+8$

$\Rightarrow \frac{d s}{d t}=3 t^{2}-12 t+9$

Initial velocity $=$ Velocity at $t=0$

$\Rightarrow \frac{d s}{d t}=3(0)^{2}-12(0)+9$

$\Rightarrow \frac{d s}{d t}=9$ units/unit time