Real Analysis: product of convergent sequences

This will lead to a contradiction and prove the original statement.In summary, if two sequences {an} and {bn} have the properties that {an} converges to a non-zero limit A and {(an)(bn)} converges, then {bn} must also converge. This can be proven by contradiction by starting with the definition of convergence and taking the logical NOT of the statement, leading to a contradiction and proving the original statement.
  • #1
uva123
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Homework Statement



suppose {an} and {bn} are sequences such that {an} converges to A where A does not equal zero and {(an)(bn)} converges. prove that {bn} converges.


Homework Equations



What i have so far:
(Note:let E be epsilon)
i know that if {an} converges to A and {bn}converges to B then {(an)(bn)} converges to AB.

Let {(an)(bn)}converge to a limit, call it L. E > 0 is given, there exists a positive integer N such that n>N implies
|(an)(bn) − L| < E


The Attempt at a Solution



how can i prove that if the product of two sequences is a convergent sequence, then the two multiplies sequences are also convergent? i think i need to prove this with a contradiction but i don't know why if {an} is convergent, {bn} can't be divergent...what does it mean if it is divergent?
please help any way you can!
 
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  • #2
for proof by contradiction, start with the definition of convergence and take the logical NOT of the statement
 
Last edited:

1. What is the definition of a convergent sequence?

A sequence is said to be convergent if the terms in the sequence approach a single limit value as the index increases. In other words, the terms in the sequence get closer and closer to a fixed value as the index increases.

2. Can the product of two convergent sequences also be convergent?

Yes, the product of two convergent sequences can also be convergent. This is because the limit of the product of two sequences is equal to the product of their individual limits.

3. What happens if one of the sequences in the product is divergent?

If one of the sequences in the product is divergent, then the product sequence will also be divergent. This is because the limit of a product containing a divergent sequence does not exist.

4. Is the product of two convergent sequences always a convergent sequence?

No, the product of two convergent sequences is not always a convergent sequence. It is only convergent if both sequences have finite limits.

5. How can we prove that the product of two convergent sequences is convergent?

In order to prove that the product of two convergent sequences is convergent, we can use the epsilon-delta definition of a limit. We can show that the limit of the product sequence is equal to the product of the limits of the individual sequences by using the properties of limits.

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