From this question, i understand that i must integrate "v" to find the displacement equation. But i thought that when you integrate, there had to be a "+C" in the equation. In the answer i was given, "C" was equal to zero. Can someone please justify this. thanks.

Question:

The velocity, after t seconds, of a particle is given in metres per second by

v = 3t^2 +1.Find distance travelled by the particle in the first 4 seconds.

Thank you.