Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Appendix C - Induction and the Binomial Theorem - Exercises - Page A15: 6

Answer

$n! \gt 2^n $ is true for $n \geq 4$

Work Step by Step

We need to prove that $n! \gt 2^n $ for $n \geq 4$ 1. Our aim is to find that $P(n)$ is true for $n=4$ $4! \gt 2^4 \implies 24 \gt 8$ So, it is true for $n=4$. 2. Our aim is to find that $P(n)$ is true for $n=k$.This, it will also true for $n=k+1$ $(k+1) ! \gt 2^{k+1} \implies (k+1)(2^k) \gt 2^k (2) $ This yields: $ k+1 \gt 2$ So, it is true for $n=k+1$. Therefore, $n! \gt 2^n $ is true for $n \geq 4$
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