Question

Aranjamente de n luate cate 1 + aranjamente de n luate cate 2 = 144

Answer 1

se poate folosi formula aranjamentelor
n!/(n-1)! + n!/(n-2)! = 144
[(n-1)!*n] / (n-1)! + [(n-2)!*(n-1)*n] / (n-2)! = 144
n + n(n-1) = 144
n^2 - n + n = 144
n= radical din 144
n= 12
S = {12}