The Student Room Group
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>

AS Level Sequences and Series - Can Someone Please Help?

calculate the following

(The sum of ) Sigma r ( r +1 ) r = 0 to r = n.

r = 0 is on the bottom of the sigma sign and n is on top) I have to calculate this and the answer I believe to be = 112, but I'm not sure how to do this 1 if someone could please help me on this 1. I'd be grateful.

Thanks
Dominic G :smile:
Reply 1
Avatar for Phichi
Phichi
11
You're summing up to n, you won't be getting a integer value out. It'll be in terms of n. You need to expand the brackets to r^2+r, then split up the terms, and use your identities for r^2 and r, in your formula book, brain, or notes. If you wish to receive an answer of 112, you'd need to be going from 0 to some integer, not n.
Reply 2
Avatar for james22
james22
16
You seem to have done the sum for n=6, you need to do it for general n. The above post explains how.

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you