Algebra and Trigonometry 10th Edition

Published by Cengage Learning
ISBN 10: 9781337271172
ISBN 13: 978-1-33727-117-2

Chapter 11 - 11.6 - Counting Principles - 11.6 Exercises - Page 823: 3



Work Step by Step

$_nP_r=\frac{n!}{(n-r)!}$ First choice: $n$ possibilities Second choice: $n-1$ possibilities Third choice: $n-2$ possibilities .... $r$th choice: $n-(r-1)$ possibilities Using the Fundamental Counting Principle: $n(n-1)(n-2)...[n-(r-1)]=n(n-1)(n-2)...[n-(r-1)]·\frac{(n-r)!}{(n-r)!}=\frac{n!}{(n-r)!}$
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