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Combinări de n luate câte n-2?

Răspuns :

[tex]C_{n}^{n-2}=\frac{n!}{(n-2)!(n-n+2)!} =\frac{n!}{2(n-2)!} =\frac{(n-2)!(n-1)n}{2(n-2)!} =\frac{n(n-1)}{2}[/tex]

Cam asa