Question

sa se rezolve ecuatia:
Cn luate cate 2+An+1 luate cate3=6, n apartine N*,n mai mare sau egal decat 2
urgenttttttttt​

Answer 1

Răspuns:

Explicație pas cu pas:

Combinatorica, ecuatie ce contine combinari si aranjeri. Din conditie rezulta

n ≥2, n+1≥3, si n∈N,

$C_{n}^{2}+A_{n+1}^{3}=6,~\frac{n!}{2!*(n-2)!} +\frac{(n+1)!}{(n+1-3)!} =6,~\frac{(n-2)!*(n-1)*n}{2!*(n-2)!}+\frac{(n+1)!}{(n-2)!} =6,~ \frac{(n-1)*n}{2}+\frac{(n-2)!*(n-1)*n*(n+1)}{(n-2)!} =6,~ \frac{(n-1)*n}{2}+(n-1)*n*(n+1)=6~|*2,~(n-1)*n+2*(n-1)*n*(n+1)=12,~n(n-1)*(1+2(n+1))=12,~(n-1)*n*(2n+3)=12, ~$

nu are solutie naturala....  ceva nu e corect in ecuatia scrisa...