.
It is not converged.
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Comment from student: Hi you say (- 1)^r - 1 is divergent yet (- 1)^r - 1 x b can be proved convergent if b > 0
This can be easily seen if b = 1/n...now if b = 1 the above doesn't change yet you claim it is still convergent..can you explain why?
Best wishes,thx,Colin
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My response.
1) Yes, the series { } with the constant b, |b| < 1, is converged. It is geormetric progression, by the way.
2) Yes, the series is not converged. It is diverged.
These two series are different. They are not the same. Do not miss them.
Different series have different properties.
3) Read these two links
https://en.wikipedia.org/wiki/Convergent_series
and
http://tutorial.math.lamar.edu/Classes/CalcII/ConvergenceOfSeries.aspx
(example 3).