Use integration by parts to solve the following integrals:

(I don't know how to do an integral sign on this lol)

[integral] x^2 sin(3x) dx.

Now, I've solved it out and come to the conclusion:

[-x^2/3 cos(3x)] + [2x/9 sin(3x) + C]

However the answer I have been given is

[(2/27 - x^2/3) cos(3x)] + [2x/9 sin(3x) + C]

Similar but not quite right. Could anyone please tell me where I'm going wrong

Thanks