
3.4: Summary


• The number of $$r$$-permutations of $$n$$ objects is $$\dfrac{n!}{(n − r)!}$$.
• The number of $$r$$-combinations of $$n$$ objects is $$\binom{n}{r} = \dfrac{n!}{r!(n−r)!}$$.
• The Binomial Theorem
• Important definitions:
• permutation, $$r$$-permutation
• $$n$$ factorial
• $$r$$-combination
• $$n$$ choose $$r$$
• binomial coefficients
• Notation:
• $$n!$$
• $$\binom{n}{r}$$