Respostas

2013-09-23T12:37:39-03:00
N! = n(n-1)!
p.ex : 5! = 5.4.3.2.1 mas 4.3.2.1 = 4!, portanto 5! = 5.4!
n!4!/(n-1)!2! = n(n-1)!4.3.2! / (n-1).2!
= n.4.3
= 12n (resp)