Attachment 28734

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- July 5th 2013, 12:29 AMTrefoil2727Combination
- July 5th 2013, 12:38 AMchiroRe: Combination
Hey lavacelava.

What have you tried?

Hint: Try expanding out in terms of factorial expressions so that you get an expression in terms of n. - July 5th 2013, 01:09 AMTrefoil2727Re: Combination
I've done only this

Attachment 28735 - July 5th 2013, 01:55 AMchiroRe: Combination
nC3 = n!/[3!*(n-3)!]

(n-1)C3 = (n-1)!/[3!*(n-4)!]

nC3/(n-1)C3 = (n!/[n-1]!) * (n-4)!/(n-3)!

Hint: n! = n*(n-1)! = n*(n-1)*(n-2)! = n*(n-1)*(n-2)*(n-3)! = n*(n-1)*(n-2)*(n-3)*(n-4)! - July 5th 2013, 02:26 AMibduttRe: Combination