Conceptual question regarding sum of series

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SUMMARY

The discussion centers on the question of whether the sum of two divergent series, sum(a_n) and sum(b_n), necessarily results in a divergent series sum(a_n + b_n). It is established that this is not always the case, as demonstrated with examples where a_n = 1/n and b_n = -1/n, leading to a convergent sum of 0. Further examples, such as a_n = n and b_n = -n, reinforce that divergent series can combine to yield a convergent result.

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Homework Statement


If the sum(a_n) and the sum(b_n) are both divergent, is the sum(a_n + b_n) necessarily divergent?


The Attempt at a Solution


At first I thought it must be divergent, but then I asked, what if a_n is 1/n and b_n is -1/n... then their sum would be 0.

Does this logic make sense? And if so, would it imply that sum(a_n + b_n)=0, and is therefore convergent?
 
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Your logic is correct. We can even get simpler examples. a_n = n, b_n = -n. Each diverges individually, but a_n + b_n = 0 for every term. And yes, it implies the sum of (a_n + b_n) is 0, convergent.
 

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