here is the question:http://i.imgur.com/bpRCfjq.jpg
I think i got part A, but does someone have a good firm answer for part B?
For 1A:There are as many edges in K_n as there are subsets of both endpoints (2) that can be chosen from a set of n vertices. The number of ways to select 2 vertices from n vertices is n(n-1) / 2 aka n choose 2.
Thus the # of edges in K_n is n(n-1)/2
Is that how to "show" this?
Then for 1b.
the one part of graph has m vertices each with degree n an the other part has n vertices each with degree m..
i see that m*n = e, if make my own little graph but i don't quite see how that comes from what i said above.