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math104-f21:hw6

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math104-f21:hw6 [2021/10/09 05:40]
pzhou
math104-f21:hw6 [2026/02/21 14:41] (current)
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 4. Show that if a series $\sum_n a_n$ converges absolutely, then $\sum_n a_n a_{n+1}$ converges absolutely. 4. Show that if a series $\sum_n a_n$ converges absolutely, then $\sum_n a_n a_{n+1}$ converges absolutely.
  
-5. Give an example of divergent series $\sum_n a_n$ of positive numbers $a_n$, such that $\lim_n a_{n+1} / a_n = \lim_n a_n^{1/n} = 1$. And give an example of convergent series $\sum_n b_n$ of positive numbers $a_n$, such that $\lim_n b_{n+1} / b_n = \lim_n b_n^{1/n} = 1$.+5. Give an example of divergent series $\sum_n a_n$ of positive numbers $a_n$, such that $\lim_n a_{n+1} / a_n = \lim_n a_n^{1/n} = 1$. And give an example of convergent series $\sum_n b_n$ of positive numbers $b_n$, such that $\lim_n b_{n+1} / b_n = \lim_n b_n^{1/n} = 1$.
  
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math104-f21/hw6.1633758004.txt.gz · Last modified: 2026/02/21 14:43 (external edit)