Cauchy Sequence Homework: Show x_n is Cauchy

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SUMMARY

The discussion focuses on proving that the sequence defined by the recurrence relation x_{n+1} = 1/(3 + x_n) with initial condition x_1 = 1 is a Cauchy sequence. The key inequality established is |x_{n+1} - x_n| ≤ (1/9)|x_n - x_{n-1}|, which is crucial for demonstrating the Cauchy property. Various approaches, including induction, were considered, but the sequence's non-monotonicity posed challenges in the proof process.

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Homework Statement



Given:

[tex]x_{n+1}=\frac{1}{3+x_n}[/tex]

with
[tex]x_1=1[/tex]

Show that:

(1)

[tex]|x_{n+1}-x_n| \leq \frac{1}{9}|x_{n}-x_{n-1}|[/tex]

and (2) x_n is Cauchy.

Homework Equations





The Attempt at a Solution


I've tried different approaches (including induction) but the sequence isn't monotonically decreasing.
 
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Have you tried writing out [itex]|x_{n+1} - x_{n}|[/itex] using the definition [itex]x_j = 1/(3+x_{j-1}[/itex]?
 
Got it ty.
 

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