Sorry for double post, but I think I figured it out.

The 1st problem is complete, so the anti-derivative can be taken. However, the 2nd problem is incomplete. Threfore, the 3 has to put to the left of (in the linear factor to the right of the integrand), to make which is the derivative of .

So now the 2nd equation is complete and the anti-derivative can be taken. Of course, when you complete an integration problem, then you also have to flip the 3 and put the result in front of the integrand (for some balancing reason).