Question

Question #c0cfe

Answer 1

`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`.