Solving the Pigeonhole Problem with f(x) for n Elements

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SUMMARY

The discussion focuses on solving the Pigeonhole Problem using a one-to-one function f from the set X = {1, 2, ..., n} onto itself. It establishes that for the k-fold composition of f, denoted as f^k, there exist distinct positive integers i and j such that f^i(x) = f^j(x) for all x in X. This conclusion is derived from the application of the pigeonhole principle, which asserts that with a finite number of functions and an infinite number of compositions, at least two compositions must yield the same result.

PREREQUISITES
  • Understanding of one-to-one functions and their properties
  • Familiarity with the pigeonhole principle
  • Basic knowledge of function composition
  • Concept of finite versus infinite sets
NEXT STEPS
  • Study the implications of the pigeonhole principle in combinatorial mathematics
  • Explore the properties of one-to-one functions in more depth
  • Learn about function composition and its applications in various mathematical contexts
  • Investigate examples of finite and infinite sets in set theory
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Homework Statement


Let f be a one-to-one function from X = {1,2,...n} onto X. Let f k = f(f(f(...f(x))) be the k-fold composition of f with itself. Show that there are distinct positive integers i and j such that f i (x) = f j (x) for all x in X.


Homework Equations


pigeonhole principle?


The Attempt at a Solution


The section is on counting and the pigeonhole principle. But I'm not sure how to start this one.
 
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Pigeonhole principle, yes. There are only a finite number of possible functions from X->X, yes? There are an infinite number of k's in the set of functions {f^k} for all k. That's a finite number of pigeonholes for an infinite number of k's. Two of the k's must be the same function.
 

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