Chapter 1: Problem 6
Test the following series for convergence. $$\sum_{n=1}^{\infty} \frac{(-1)^{n} n}{n+5}$$
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Chapter 1: Problem 6
Test the following series for convergence. $$\sum_{n=1}^{\infty} \frac{(-1)^{n} n}{n+5}$$
These are the key concepts you need to understand to accurately answer the question.
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Get started for freeThe following alternating series are divergent (but you are not asked to prove this). Show that \(a_{n} \rightarrow 0 .\) Why doesn't the alternating series test prove (incorrectly) that these series converge? (a) \(\quad 2-\frac{1}{2}+\frac{2}{3}-\frac{1}{4}+\frac{2}{5}-\frac{1}{6}+\frac{2}{7}-\frac{1}{8} \cdots\) (b) \(\quad \frac{1}{\sqrt{2}}-\frac{1}{2}+\frac{1}{\sqrt{3}}-\frac{1}{3}+\frac{1}{\sqrt{4}}-\frac{1}{4}+\frac{1}{\sqrt{5}}-\frac{1}{5} \cdots\)
Use Maclaurin series to do and check your results by computer. $$\lim _{x \rightarrow 0}\left(\frac{1+x}{x}-\frac{1}{\sin x}\right)$$
Find the first few terms of the Maclaurin series for each of the following functions and check your results by computer. $$\cos \left(e^{x}-1\right)$$
Prove that an absolutely convergent series \(\sum_{n=1}^{\infty} a_{n}\) is convergent. Hint: Put \(b_{n}=\) \(a_{n}+\left|a_{n}\right| .\) Then the \(b_{n}\) are nonnegative; we have \(\left|b_{n}\right| \leq 2\left|a_{n}\right|\) and \(a_{n}=b_{n}-\left|a_{n}\right|.\)
Show that \(n ! > 2^{n}\) for all \(n > 3\). Hint: Write out a few terms; then consider what you multiply by to go from, say, \(5 !\) to \(6 !\) and from \(2^{5}\) to \(2^{6}\).
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