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A choose b

Revision as of 16:55, 15 June 2019 by Colball (talk | contribs)

Here is the formula for a choose b: $\binom{a}{b}=\frac{a!}{b!(a-b)!}$. This is assuming that of course $a \ge b$.

Why is it important?

a choose b counts the number of ways you can pick b things from a set of a things. For example $\binom{8}{2}=\frac{8!}{2!(8-2)!}=\frac{8(7)}{2}=\frac{42}{2}=21$. More at https://artofproblemsolving.com/videos/counting/chapter4/64.

a choose 2

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