Questions
Question 1
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What condition on \(a_n\) makes \(\sum a_n\) a positive series in this topic?
Question 2
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If \(a_n\ge0\), what inequality relates \(S_{N+1}\) and \(S_N\)?
Question 3
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State whether \(\sum_{n=1}^{\infty}1/n^2\) has non-negative terms.
Question 4
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Explain why the partial sums of \(\sum_{n=1}^{\infty} e^{-n}\) are increasing.
Question 5
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Find \(S_3\) for the positive series \(\sum_{n=1}^{\infty}1/n^2\).
Question 6
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If \(0\le S_N\le 7\) for every \(N\) and \(S_N\) is increasing, what can you conclude?
Question 7
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Explain why \(\sum_{n=1}^{\infty}n^2\) diverges as a positive series.
Question 8
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For \(a_n=1/(n^2+1)\), show the partial sums are increasing.
Question 9
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Use comparison to show \(\sum_{n=1}^{\infty}1/2^n\) is bounded above.
Question 10
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Show that \(\sum_{n=1}^{\infty}1\) diverges using positive-series partial sums.
Question 11
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Explain why increasing partial sums do not automatically mean divergence.
Question 12
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Why does proving \(S_N\le M\) for all \(N\) matter for a positive series?
Question 13
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Show that if \(0\le a_n\le 1/2^n\), then \(\sum a_n\) converges.
Question 14
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Suppose \(a_n\ge 1/n\) for all \(n\). What can you conclude about \(\sum a_n\) if all terms are non-negative?
Question 15
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For \(a_n=p^n\) with \(p\ge0\), determine for which \(p\) the positive series \(\sum_{n=1}^{\infty}a_n\) converges.
Question 16
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If \(a_n\ge0\) and the partial sums satisfy \(S_{2N}\le4\) for every \(N\), prove the whole series converges.
Question 17
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A detector adds positive noise energies \(E_n\ge0\). If \(\sum_{n=1}^{N}E_n\le0.05\) for every \(N\), what does this imply?
Question 18
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Diagnose the error: positive partial sums increase, so every positive series diverges.
Question 19
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Prove that a positive series cannot have decreasing partial sums unless all new terms are zero.
Question 20
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A positive series has partial sums \(S_N=2-1/N\). Explain why this is consistent with convergence but cannot describe partial sums starting at \(N=1\) for strictly positive terms.