Clip@@ nht k vng anh video nht k vng anh hong thu linh nht k vng anh nm bao nhiu jpb
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2025-09-19 02:56:47
The theorem that $\binom {n} {k} = \frac {n!} {k! (n-k)!}$ already assumes $0!$ is defined to be $1$. Otherwise this would be restricted to $0