MHB Looking for a recursion relation

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    Recursion Relation
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The discussion centers on a specific non-linear recursion relation, f(n + 1) = 2 - d(n)/f(n), where d(n) is arbitrary. The equation may lack a closed-form solution due to its non-linearity, leading to challenges in finding general conclusions. Alternative representations include a non-linear difference equation and a continued fraction approach. Participants agree that while a general solution is elusive, numerical methods could provide insights. The equation remains a complex and frustrating problem for those involved.
topsquark
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I don't know how to do a search for information on a specific equation. It's [math]f(n + 1) = 2 - \dfrac{d(n)}{f(n)}[/math], where d(n) is more or less arbitrary. It came up in some work I've been doing and I can't seem to get anywhere with it. Being non-linear it may not even have a closed form solution. There are two other ways to look at it. It's a non-linear difference equation: [math]f \Delta f + f(f - 2) = d[/math] and it can also be considered as a continued fraction. (I'm going to be looking up that idea tonight.)

Any thoughts?

-Dan
 
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topsquark said:
Any thoughts?
Yes, I think that it is impossible to make any general conclusions as the answer depends completey on ## d(n) ##.
 
Yes, thank you. I have found (but not proven) that this equation cannot be solved in general. I haven't even found a general way to approach it. It is a very annoying little equation!

-Dan

Addendum: Well, I should say "does not have closed form solutions in general." We can always do it numerically.
 
Here is a little puzzle from the book 100 Geometric Games by Pierre Berloquin. The side of a small square is one meter long and the side of a larger square one and a half meters long. One vertex of the large square is at the center of the small square. The side of the large square cuts two sides of the small square into one- third parts and two-thirds parts. What is the area where the squares overlap?

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