@Preben Alsholm 

Thanks.

Yes, N1 and N3 are constants, but I would like them to be determined from the other boundary conditions, and the only way of doing so that I could think of was to have them solved for.

Rewriting the first equation looks interesting... I suppose I could then 'force' the solution into one of the branches by writing out only the positive/negative root, couldn't I?

How would I deal with the constant of integration, C, other than having it solved for (like N1 and N3)?

@Preben Alsholm 

Thanks.

Yes, N1 and N3 are constants, but I would like them to be determined from the other boundary conditions, and the only way of doing so that I could think of was to have them solved for.

Rewriting the first equation looks interesting... I suppose I could then 'force' the solution into one of the branches by writing out only the positive/negative root, couldn't I?

How would I deal with the constant of integration, C, other than having it solved for (like N1 and N3)?