Proving Cauchy Sequence: a_n = [a_(n-1) + a_(n-2)]/2

In summary, a Cauchy Sequence is a mathematical sequence where the terms get closer and closer together as the sequence progresses. To prove that a sequence is Cauchy, one must show that the difference between any two terms in the sequence becomes smaller and smaller as the sequence progresses. The formula for this particular Cauchy Sequence is a_n = [a_(n-1) + a_(n-2)]/2, and it has significance in the study of mathematical analysis and number theory. It can converge to any number as its limit.
  • #1
ricardianequiva
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0

Homework Statement


Prove that the following sequence is Cauchy:
a_n = [a_(n-1) + a_(n-2)]/2 (i.e. the average of the last two), where
a_0 = x
a_1 = y


Homework Equations


None


The Attempt at a Solution


I was trying to use the definition of Cauchy (i.e. |a_m - a_n| < e) by relating a_n - a_(n-1) to a_(n-1) - a_(n-2), but to no avail.
 
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  • #2
can you use the theorem: every convergent sequence, is a cauchy sequence

just prove the sequence converges, cite the theorem, and you're finished
 

1. What is a Cauchy Sequence?

A Cauchy Sequence is a type of mathematical sequence where the terms get closer and closer together as the sequence progresses. It is named after the French mathematician Augustin-Louis Cauchy.

2. How do you prove that a sequence is Cauchy?

To prove that a sequence is Cauchy, you must show that for any small positive number, there exists a point in the sequence after which all terms are within that distance from each other. This can be done by showing that the difference between any two terms in the sequence becomes smaller and smaller as the sequence progresses.

3. What is the formula for the Cauchy Sequence a_n = [a_(n-1) + a_(n-2)]/2?

The formula for this particular Cauchy Sequence is a_n = [a_(n-1) + a_(n-2)]/2. This means that each term in the sequence is equal to the average of the two preceding terms. For example, if a_1 = 1 and a_2 = 2, then a_3 = (1+2)/2 = 1.5, a_4 = (2+1.5)/2 = 1.75, and so on.

4. What is the significance of the Cauchy Sequence a_n = [a_(n-1) + a_(n-2)]/2?

This particular Cauchy Sequence has significance in the study of mathematical analysis and number theory. It is also used in various other areas of mathematics, such as in the proof of the Central Limit Theorem in statistics.

5. Can the Cauchy Sequence a_n = [a_(n-1) + a_(n-2)]/2 converge to any number?

Yes, the Cauchy Sequence a_n = [a_(n-1) + a_(n-2)]/2 can converge to any number. This is because the sequence gets closer and closer together as it progresses, meaning that it can approach any number as its limit.

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