I'm not sure if you meant 3-->0 or 0-->3 So I'll just show you how to get the integral and you can commute the answer.
Familiarize yourself with some of common integral formats. These can be found in your text book or online review sheets. If you can remember these it makes things a lot easier.
Common integral format:
∫ 1/(a2 + u2) du = (1/a)tan-1(u/a) + C
Since the integral is defined on 3-->0 you can ignore the constant C.
2 ∫ 1/(32 + x2) dx = (2/3)tan-1(x/3)
Then calculate from x = 3 to 0