# Sigma notation factorials

• Nov 25th 2012, 11:30 AM
minicooper58
Sigma notation factorials
Hi , I'm totally lost on this question and answer attached . Please the full simplified working for both parts would be greatly appreciated .

Thank you
• Nov 25th 2012, 11:50 AM
coolge
Re: Sigma notation factorials
1. (r+1)! - (r-1)! = (r+1)r(r-1)! - (r-1)! Take (r-1)! as common factor and simplify.

2. Just expand : 2! - 0! +
3! - 1! +
4! - 2! +
......
(n-1)! - (n-2)! +
n! - (n-2)! +
(n+1)! - (n-1)!

Cancel the terms ans add the rest.
• Nov 25th 2012, 12:57 PM
minicooper58
Re: Sigma notation factorials
Hi , thank you for part a) and the terms in b) but I am still struggling with how they arrive at the proof given after cancelling the terms .
Any help would be appreciated .

Thank you
• Nov 25th 2012, 01:02 PM
coolge
Re: Sigma notation factorials
The terms that are not cancelled are (n+1)! + n! - 1! -0! = n!(n+1+1) - 2. Hope this helps!
• Nov 25th 2012, 02:56 PM
topsquark
Re: Sigma notation factorials
Quote:

Originally Posted by minicooper58
Hi , I'm totally lost on this question and answer attached . Please the full simplified working for both parts would be greatly appreciated .

Thank you

Please show some of you own work on the problem before you post the question. This is not a homework answering service.

-Dan