I have an exam coming up that I'm studying for and I'm somewhat stumped by a couple problems. I need to derive an asymptotically tight bound for the following summation:
Assume $r$ and $s$ are constants such that $r,s\geq 0$.
So far I have come up with
However, I'm getting told these are not asymptotically tight bounds and I need to correct this answer. Can anyone assist?