Question

Aranjamente de n luate cate 1 plus combinări de n luate cate 1 ,egal cu 8

Answer 1

An|1  = n
Cn|1 n/1! = n
n + n = 2n = 8 => n=4

Answer 2

n!/(n-1)!+n!/(n-1)!*1!=n+n
2n=8
n=4
as simple as that!!