# n choose k

• May 9th 2011, 12:45 PM
math321
n choose k
n chooses k n on top k below in brackets
what that means

like 75 on top 3 below in brackets
• May 9th 2011, 12:47 PM
mr fantastic
Quote:

Originally Posted by math321
n chooses k n on top k below in brackets
what that means

like 75 on top 3 below in brackets

Surely it is defined in your textbook or class notes! Out of interest, where have you met this notation ....?
• May 9th 2011, 12:47 PM
TheEmptySet
$\binom{n}{k}=\frac{n!}{(n-k)!k!}$

$\binom{75}{3}=\frac{75!}{(72)!3!}$
• May 9th 2011, 01:17 PM
Plato
Quote:

Originally Posted by math321
n chooses k n on top k below in brackets
what that means like 75 on top 3 below in brackets

Do you mean this
$\left\{ {\begin{array}{*{20}c} n \\ k \\ \end{array} } \right\}$ and not $\binom{n}{k}~?$