Sequences - factorial r, !

1. Nov 14, 2003

martinrandau

Can anybody help me solving this?

Write in terms of factorials

n((n^2)-1)

(n+1)!/(n-2)!

but I don't know how to get there, and since it's week- end I have no chance to ask anyone teachers, etc.
//Martin

2. Nov 14, 2003

Guybrush Threepwood

n(n2-1) = n(n-1)(n+1)

3. Nov 14, 2003

martinrandau

4. Nov 14, 2003

Tom Mattson

Staff Emeritus
I'll give you a hint.

Expand the numerator and denominator of the above ratio and cancel the factors common to both. For instance, the numerator is:

(n+1)!=(n+1)(n)(n-1)(n-2)...

Get the idea?

5. Nov 14, 2003

Yes!
Thank you!

//Martin