Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 11 - Counting Methods and Probability Theory - 11.2 Permutations - Exercise Set 11.2 - Page 701: 58

Answer

n! is obtained by multiplying all numbers from n down to 1.

Work Step by Step

See Factorial Notation, page 696. $n!=n(n-1)(n-2)\cdots(3)(2)(1)$ and, by definition, $0!=1$ So if n is a positive integer, n! is obtained by multiplying all numbers from n down to 1.
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