Răspuns:
Explicație pas cu pas:
Combinatorica, ecuatie ce contine combinari si aranjeri. Din conditie rezulta
n ≥2, n+1≥3, si n∈N,
[tex]C_{n}^{2}+A_{n+1}^{3}=6,~\frac{n!}{2!*(n-2)!} +\frac{(n+1)!}{(n+1-3)!} =6,~\frac{(n-2)!*(n-1)*n}{2!*(n-2)!}+\frac{(n+1)!}{(n-2)!} =6,~ \frac{(n-1)*n}{2}+\frac{(n-2)!*(n-1)*n*(n+1)}{(n-2)!} =6,~ \frac{(n-1)*n}{2}+(n-1)*n*(n+1)=6~|*2,~(n-1)*n+2*(n-1)*n*(n+1)=12,~n(n-1)*(1+2(n+1))=12,~(n-1)*n*(2n+3)=12, ~[/tex]
nu are solutie naturala.... ceva nu e corect in ecuatia scrisa...