A Surjective function from [0,1]\{1/2} to [0,1]

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SUMMARY

The discussion centers on the existence of a surjective function from the interval [0,1]\{1/2} to [0,1} that preserves order, specifically that if f(a) > f(b), then a > b. Participants explore the implications of an increasing sequence approaching 1/2 and its limit under the function f. The conclusion drawn is that the limit of f(x_n) cannot be in the range of f, indicating that such a surjective function cannot exist under the given constraints.

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  • Understanding of surjective functions in mathematics
  • Familiarity with the concept of limits in sequences
  • Knowledge of discrete mathematics principles
  • Basic comprehension of interval notation and properties
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  • Research the properties of surjective functions in real analysis
  • Study the implications of limits in sequences and their mappings
  • Explore the concept of order-preserving functions
  • Investigate counterexamples in discrete mathematics related to function mappings
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Students of discrete mathematics, mathematicians exploring function theory, and anyone interested in the properties of surjective functions and their limitations.

Ella1
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Hello guys! I'm taking Discrete Mathematics this semester and I got this question in one of my homework tasks.
I've tried thinking about the solution over and over but can't seem to come up with anything..
The question goes like this: Is there a Surjective function from [0,1]\{1/2} to [0,1] such that if f(a)>f(b) that means that a>b?
I must mention that sadly I cannot use any arguments involving cardinality..
Any clue that might help will save my life!p.s Sorry for my poor English :)!
 
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Ella said:
Hello guys! I'm taking Discrete Mathematics this semester and I got this question in one of my homework tasks.
I've tried thinking about the solution over and over but can't seem to come up with anything..
The question goes like this: Is there a Surjective function from [0,1]\{1/2} to [0,1] such that if f(a)>f(b) that means that a>b?
Hi Ella, and welcome to MHB!

Suppose that $(x_n)$ is an increasing sequence in $[0,1/2)$, with $\lim_{n\to\infty}x_n = 1/2.$ What can you say about the point $\lim_{n\to\infty}f(x_n)$? Can it be in the range of $f$?
 

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