Proving Convergence: Showing That x_n and y_n Have the Same Limit

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Homework Help Overview

The discussion revolves around proving that if a sequence \( x_n \) converges, then the sequence defined by its average values \( y_n = \frac{x_1 + x_2 + ... + x_n}{n} \) also converges to the same limit. Participants are exploring the relationship between the convergence of \( x_n \) and \( y_n \).

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to establish that if \( x_n \) converges to a limit \( P \), then \( y_n \) must also converge to \( P \). They question whether they need to show that \( |y_n - P| < \epsilon \). Other participants discuss the definition of convergence and suggest manipulating the sum of the sequence to explore its properties.

Discussion Status

Participants are actively engaging with the problem, with some providing hints and guidance on how to approach the proof. There is a focus on defining limits and exploring the implications of convergence, though no consensus has been reached on the specific steps to take.

Contextual Notes

Participants are working under the constraints of a homework assignment, which may limit the information they can use or the methods they can apply. The discussion includes assumptions about the behavior of convergent sequences and the properties of limits.

cragar
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Homework Statement


Show that if x_n is a convergent sequence, then the sequence given by that average values also converges to the same limit.
y_n=\frac{x_1+x_2+x_3+...x_n}{n}

The Attempt at a Solution


Should I say that x_n converges to some number P. so now I need to show that
y_n converges to P as well.
Do I need to show that y_n-P&lt; \epsilon
 
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That's exactly what you need to show. Got any ideas?
 
so x_n is my nth term right, and also what the limit converges to.
So x_n=P
So I should have(x_1+x_2+x_3+...P)=Pn maybe I can work on manipulating the sum and see if certain parts are less than other parts.
 
Let me give you a hint:

Define the limit of x_n to be L then there is (for every epsilon>0) a N such that for n &gt; N

|x_n-L|&lt; \epsilon

Now we get:

\left| \frac{x_1+x_2+x_3+...+x_n}{n} -\frac{nL}{n} \right| = \frac{|x_1-L| +|x_2-L| +...+|x_n-L|}{n} =\frac{|x_1-L| +|x_2-L| +...+|x_N-L| + |x_{N+1}-L|+...+|x_n-L|} {n} &lt; \frac{|x_1-L| +|x_2-L| +...+|x_N-L|}{n} + \frac{(n-N)}{n} \epsilon &lt; ...

Can you fill in the dots at the end?
 

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