I am trying to understand the following question:
For each of the following functions $f_i$, find the simplest function $g_i$ such that $f_i(n) = Θ(g_i(n))$
two examples:
(b) $f_2(n) = n + n * log(n) + \sqrt{n}$
(c) $f_3(n) = log_2(n^{20}) + (log_2n)^{10}$
I understand the chain of dominance, such that $n*log(n)$ and $(log_2n)^{10}$ are the two dominant elements of each function respectively. So they could upper bound $f$, but I don't understand how to find lower bound and then what to do with the upper/lower bound once I've found it. I understand finding equivalence classes, but not then creating functions to represent them.
Any hints or explanations of how to go about this question would be very much appreciated!