Okay, so I have this equation:

$\displaystyle a_n=[d(n-b)]+a$

and I need to get to

$\displaystyle a_n=(a/b)+d(n-1)$

I've tried going about this a couple of times, but I always end up looping back to a previous step. If anyone could get me started in the right direction, that'd be great. I'm not even asking for a complete solution, just maybe the first few lines. Is this type of literal equation possible to do? I know how to do these equations, it's just this one that I'm having difficulty with.

Also note that this is part of a larger problem, so if more information is needed, it can be provided.