Ok there are a bunch of nice physics formulas called the kinematic equations which are great for this stuff, but I'm sure you're supposed to derive it through calculus.

So you start with . Integrate that dt and you should get . What is C1? It's the initial velocity. You now have a velocity function. Integrate once more and you should get . What is C2? That's the initial displacement. You now have a position function. Plug and chug.

How does that look?