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## Homework Statement

Let an be a series of positive elements such as lim_n->infinity_an=0 and the series Sigma_n=1-infinity_an diverge.

Let bn=(-1)^n*an

Prove or find counterexamples for the next propositions:

1. 1. Sigma_bn diverge.

2. Sigma_bn doesn't absolutely converge.

3. Sigma_bn converge.

## Homework Equations

## The Attempt at a Solution

I need a counterexample for 3...I have a counterexample for 1 and I think I can prove 2...

3 is all I need

TNX everyone!