Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 9 - Infinite Series - 9.1 Sequences - Exercises Set 9.1 - Page 605: 20

Answer

$1;1.1622777;1.2426407; 1.2915026;1.3245553$ Converges to $\frac{3}{2}$.

Work Step by Step

Plugging $n = {1,2,3,4,5}$ in $\sqrt {n^2+3n}-n$. $\implies n=1$: $\sqrt {(1)^2+3(1)}-1=1$ $\implies n=2$: $\sqrt {(2)^2+3(2)}-2=1.1622777$ $\implies n=3$: $\sqrt {(3)^2+3(3)}-3=1.2426407$ $\implies n=4$: $\sqrt {(4)^2+3(4)}-4=1.2915026$ $\implies n=5$: $\sqrt {(5)^2+3(5)}-5=1.3245553$ We see that $\lim\limits_{n \to \infty} (\sqrt {n^2+3n}-n)=\lim\limits_{n \to \infty} \dfrac{3n}{\sqrt {n^2+3n}+n}\\=\lim\limits_{n \to \infty} \dfrac{3}{\sqrt{1+3/n}+1}=\dfrac{3}{2}$ Therefore, the given series converges to $\frac{3}{2}$.
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