Does bn Converge to Zero if an Diverges and an*bn Converges?

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SUMMARY

The discussion centers on the mathematical proof that if the sequence \( a_n \) diverges to infinity and the product sequence \( a_n b_n \) converges to a limit \( L \), then the sequence \( b_n \) must converge to zero. The key argument involves using the definitions of convergence and divergence, specifically that for any \( \epsilon > 0 \), there exists an \( N_1 \) such that for \( n > N_1 \), \( |a_n b_n - L| < \epsilon \), and an \( N_2 \) such that for \( n > N_2 \), \( a_n > X \) for any \( X > 0 \. By selecting \( n \) greater than both \( N_1 \) and \( N_2 \), one can demonstrate that \( b_n \) must approach zero.

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Homework Statement



If sequence an diverges to infinity and sequence an*bn converges then how do I prove that sequence bn must converge to zero?


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The Attempt at a Solution


I really don't know how to go about this so any help would be so appreciated.
Thanks
 
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If a_nb_n converges, to, say L, then, given any \epsilon&gt; 0, there exist N_1 such that if n&gt; N_1, |a_nb_n- L|&lt; \epsilon.

Since a_n diverges to infinity, then, given any X>0, there exist N_2 such that if n&gt; N_2, a_n&gt; X.

Take n greater than the larger of N_1 and N_2 and use both of those.
 

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