Question 253879: Could you please help me with the following question?
Show that if n > 1, then P(n,2)=nē-n
Answer by jim_thompson5910(35256)   (Show Source):
You can put this solution on YOUR website! P(n,r)=n!/(n-r)! ... Start with the permutation formula
P(n,2)=n!/(n-2)! ... Plug in r=2
P(n,2)=[n(n-1)(n-2)!]/(n-2)! ... Rewrite n! as n(n-1)(n-2)!
P(n,2)=n(n-1) ... Cancel out the common terms (n-2)!
P(n,2)=n^2-n ... Distribute
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