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comparison test (Theorem)

The series

$\displaystyle \sum_{i=0}^\infty a_i$
with real $ a_i$ is absolutely convergent if there is a sequence $ (b_n)_{n\in\mathbb{N}}$ with positive real $ b_n$ such that
$\displaystyle \sum_{i=0}^\infty b_i$
is convergent and for all sufficiently large $ k$ holds $ \vert a_k\vert\leq b_k$.

Also, the series $ \sum a_i$ is divergent if there is a sequence $ (b_n)$ with positive real $ b_n$, so that $ \sum b_i$ is divergent and $ a_k\geq b_k$ for all sufficiently large $ k$.



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proof of comparison test (Proof) by mathwizard
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Cross-references: divergent, positive, sequence, absolutely convergent, real, series
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This is version 1 of comparison test, born on 2003-01-10.
Object id is 3889, canonical name is ComparisonTest.
Accessed 3460 times total.

Classification:
AMS MSC40A05 (Sequences, series, summability :: Convergence and divergence of infinite limiting processes :: Convergence and divergence of series and sequences)

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