Question #c0cfe

1 Answer
Jan 23, 2015

#sum _"n=3" ^7 9+4n^2+4=#

#sum _"n=3" ^7 4n^2+13#

These are 5 terms to be added. And you are on the right way, but you forgot to add the #5*13=65#

Actually, I think it strange that the #9# and #4# are separated. I suspect one of them had a #n# attached to it in the original problem.
You always calculate the full expression, for every value of #n# from #3# up to (and including) #7#.