- #1
knowLittle
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Homework Statement
Determine whether the series is absolutely convergent, conditionally convergent, or divergent.
##\sum _{n=1}\left( -1\right) ^{n}\dfrac {n} {n^{2}+1}## the sum goes to infinity.
Homework Equations
Theorem for absolute convergence.
Test for divergence
The Attempt at a Solution
By the theorem of Absolute convergence: If the absolute value of the sum converges, then the sum converges.
##\sum _{n=1}\left| \left( -1\right) ^{n}\dfrac {n} {n^{2}+1}\right| =\sum \dfrac {\dfrac {1} {n}} {1+\dfrac {1} {n^{2}}}=0##
I found that it converges to zero. Now, If this was the test for divergence, the test would be inconclusive. Since it is the absolute convergence theorem, the sum without the absolute value also converges.
Is this reasoning correct?
Thank you.