Question

So I got this problem.
http://screencast.com/t/BYYo2dwwz

Leave the part where it has to be a program. I Just can't understand what is asking me in mathematical terms. Can someone explain to me simply? I would really appreciate it.

EDIT: Please try to explain it to me simply, I have absolutely no clue

Answer 1

your given a series.

Answer 2

\[S _{n}=n/2[2a+(n-1)d]\]

Answer 3

where S_n is the sum of all terms

Answer 4

that doesnt make it more simple to me

Answer 5

r u familiar with that formula?

Answer 6

use the " telescopic " series