Sequences and existence of limit

In summary, the problem states that given a bounded sequence an and a limit bn as n approaches infinity, where bn is always less than or equal to half of bn-1, prove that if an+1 is greater than or equal to an minus bn, then the limit of an as n approaches infinity exists. The attempt at a solution involves defining convergence and boundedness, finding a numerical example, and using previous examples or methods to show convergence. A complete statement of the problem is needed for further analysis.
  • #1
Felafel
171
0

Homework Statement



Let an be a bounded sequence and bn such that

the limit bn as n→∞ is b and

0<bn ≤ 1/2 (bn-1)

Prove that if:

an+1 ≥ an - bn,

then

lim an
n→∞



Homework Equations





The Attempt at a Solution



no clue :(
 
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  • #2
Please provide an attempt or this thread will be locked.

It's not possible to have "no clue". There are always things you can do:

  • Write down the relevant definition such as convergence and bounded.
  • Find a numerical example.
  • What were some previous examples/problems where you had to show convergence, what were the steps you took there? Can you mimic those to an extent?
 
  • #3
Also, please write out the full problem. Writing "then [itex]\lim_{n\rightarrow +\infty} a_n[/itex]" is incomplete.
 
  • #4
oops, sorry.
i'll write a new thread (properly)
 

Related to Sequences and existence of limit

1. What is a sequence?

A sequence is a list of numbers that follow a specific pattern or rule. Each number in the sequence is called a term, and the number of terms in the sequence is infinite.

2. What is the difference between a convergent and a divergent sequence?

A convergent sequence is one that has a limit, meaning that the terms in the sequence approach a single, finite value as the sequence continues. A divergent sequence, on the other hand, does not have a limit and the terms in the sequence either approach infinity or oscillate between different values.

3. How is the existence of a limit determined in a sequence?

The existence of a limit in a sequence is determined by examining the behavior of the terms in the sequence as the index (or position) of the terms increases. If the terms approach a single, finite value, then the sequence has a limit. If the terms do not approach a single value, the sequence does not have a limit.

4. Can a sequence have multiple limits?

No, a sequence can only have one limit. If a sequence has multiple limits, it is considered divergent.

5. How is the limit of a sequence calculated?

The limit of a sequence can be calculated by examining the behavior of the terms in the sequence and using mathematical methods such as the squeeze theorem, the monotone convergence theorem, or the ratio test. In some cases, the limit may be easily determined by simply looking at the pattern of the terms in the sequence.

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