Particle Motion Initial Value Problem

A particle moves along the $x$-axis with acceleration $a(t) = 6\cos 3t$ for time $t \geq 0$. If the velocity of the particle at $t=0$ is $v(0)=-2$ and its position at $t=0$ is $x(0)=4$, then the position of the particle at time $t$ is $x(t) =$