University Calculus: Early Transcendentals (3rd Edition)

Published by Pearson
ISBN 10: 0321999584
ISBN 13: 978-0-32199-958-0

Chapter 9 - Section 9.10 - The Binomial Series and Applications of Taylor Series - Practice Exercises - Page 553: 82


Radius of convergence is: $\dfrac{5}{2}$

Work Step by Step

We need to apply the Ratio Test to the series. $\lim\limits_{n \to \infty} |\dfrac{u_{n+1}}{u_n}|=\lim\limits_{n \to \infty} |\dfrac{(2n+3) (x-1)}{5n+4}|$ or, $=|x-1| \lim\limits_{n \to \infty} (\dfrac{(2n+3)}{5n+4})$ or, $=|x-1| \lim\limits_{n \to \infty} (\dfrac{(2+3/n)}{5+4/n})$ So, $=\dfrac{2}{5}|x-1|$ The series converges absolutely for $\dfrac{2}{5}|x-1| \lt 1$ or, $|x-1| \lt \dfrac{5}{2}$ So, the radius of convergence is: $\dfrac{5}{2}$
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