Calculus: Early Transcendentals 8th Edition

Published by Cengage Learning
ISBN 10: 1285741552
ISBN 13: 978-1-28574-155-0

Chapter 11 - Section 11.1 - Sequences - 11.1 Exercises - Page 706: 89

Answer

$\lim\limits_{n\to\infty} (a_nb_n)=0$

Work Step by Step

We need to prove that $\lim\limits_{n\to\infty} (a_nb_n)=0$ Apply the property of the absolute value as follows: $-|a_n| \leq a_n \leq |a_n|$ for all the values of $n$ Let us consider that $\lim\limits_{n\to\infty} |a_n|=0$ Suppose $\lim\limits_{n\to\infty} a_n=L$ and the function $f(a_n)$ is continuous at the limit $L$. Apply the limit laws of sequences. $\lim\limits_{n\to\infty} |a_n|=0$; $\lim\limits_{n\to\infty} -|a_n|=-\lim\limits_{n\to\infty} |a_n|=0$ The squeeze theorem for a sequence states that: $\lim\limits_{n\to\infty} a_n=0$. This means that when $\lim\limits_{n\to\infty} |a_n|=0$, then we have $\lim\limits_{n\to\infty} a_n=0$ Now, let us consider a small number $\epsilon \gt 0$ , then we have $a_n \to 0$, so that there will exist a number $N$ such that $|a_n| \lt \dfrac{\epsilon }{M}$ when $n \geq N$ This gives us: $|a_nb_n|=|a_n||b_n| \lt \dfrac{\epsilon }{M} (M)=\epsilon$ Hence, it has been verified that $\lim\limits_{n\to\infty} (a_nb_n)=0$
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