Why is it that \frac{X!}{(2!)(X-2)!} - (X-1) = (\frac{X}{2} - 1)(X-1) ?
B Thread Starter boks Joined Oct 10, 2008 218 Dec 6, 2009 #1 Why is it that \(\frac{X!}{(2!)(X-2)!} - (X-1) = (\frac{X}{2} - 1)(X-1)\) ?
studiot Joined Nov 9, 2007 4,998 Dec 6, 2009 #2 The key is to multiply through by 2! This will enable you to get rid of all the factorials and the rest is simple algebra. Can you do it now?
The key is to multiply through by 2! This will enable you to get rid of all the factorials and the rest is simple algebra. Can you do it now?
J jpanhalt Joined Jan 18, 2008 11,087 Dec 6, 2009 #3 I just substituted X!/(X)(X-1) for (X-2)! and everything canceled out to give the answer. John
StayatHomeElectronics Joined Sep 25, 2008 1,073 Dec 6, 2009 #4 From the definition of factorial, X!, you write out X! as X(X-1)(X-2)(X-3)(X-4)... and (X-2)! as (X-2)(X-3)(X-4)..., simplification becomes much easier.
From the definition of factorial, X!, you write out X! as X(X-1)(X-2)(X-3)(X-4)... and (X-2)! as (X-2)(X-3)(X-4)..., simplification becomes much easier.
