giúp em với ạ!!!!
CRM:C^{0}_{n}.C^{k}_n + C^{1}_{n}.C^{k+1}_
n + C^{2}_{n}
.C^{k+2}_n +...+
C^{n-k}_{n}.C^{n}_n = \frac{(2n)!}{(n-k)!(n+k)!}
giúp em với ạ!!!!
CRM:
$C^{0}_{n}.C^{k}_
{n
}$ +
$C^{1}_{n}.C^{k+1}_{n}
$+
....
.+
$C^{n-k}_{n}.C^{n}_
{n
}$ =
$\frac{(2n)!}{(n-k)!(n+k)!}
$ (0$\leq$k$\leq $n)