Formula generala:
Aranjamente de n luate cate k = n!/(n-k)!
Combinari de n luate cate k = n!/k!(n-k)!
Aranjamente de 5 luate cate 3 = 5!/(5-3)! = 120/2 = 60
Combinari de 6 luate cate 2 = 6!/2!(6-2)! = 720/(2*4!) = 720/(2*24) = 720/48 = 15
60 - 4*15 = 60 - 60 = 0