Domains which equals to each other (1) has any significance?

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Discussion Overview

The discussion revolves around the concept of comparing the cardinality of rational numbers within different intervals, specifically between [0,1] and [1,2]. Participants explore the implications of finding bijections between these domains and question the significance of such equivalences.

Discussion Character

  • Mathematical reasoning

Main Points Raised

  • One participant notes that there are infinitely many rational numbers in both [0,1] and [1,2] and questions how to prove their equivalence in number.
  • Another participant suggests that establishing a bijection, specifically f(x)=x+1, demonstrates the equivalence of the number of rationals in the two intervals.
  • A question is raised regarding the meaning of x in this context, which is clarified to represent any number in the interval [0,1].
  • A further contribution introduces an alternative bijection, f(x)=2x, to show that the number of rationals in [0,1] is also equivalent to those in [0,2].

Areas of Agreement / Disagreement

Participants generally agree on the method of using bijections to demonstrate the equivalence of the number of rational numbers in the specified intervals, though the significance of this equivalence remains a point of inquiry.

Contextual Notes

The discussion does not resolve the significance of the equivalence of the domains or the implications of these bijections beyond the mathematical demonstration of cardinality.

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between 0-1 there are infinite number of rational numbers now between 1-2 there are also infinite number of rational numbers, how can we proove that the number of rational numbers between 0-1 equals to those between 1-2?

does the difference of the domains which equals to each other (1) has any significance?
 
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To show that the number of rationals on [0,1] is the same as the number of rationals on [1,2] you just need to find a bijection from [0,1] to [1,2].

Clearly [itex]f(x)=x+1[/itex] is a suitable bijection.
 
what is x represnts in this context? (the number of rational numbers?).
 
x represents any number in [0, 1]
 
Originally posted by master_coda
To show that the number of rationals on [0,1] is the same as the number of rationals on [1,2] you just need to find a bijection from [0,1] to [1,2].

Clearly [itex]f(x)=x+1[/itex] is a suitable bijection.
let me see if i understand, x is in [0,1] then f(x) is in [1,2] therefore f:x->f(x) therefore the number of rationals in [0,1] equals to [1,2].
 
Also, using the function f(x)=2x, one can prove the number of rationals in [0, 1] is the same as the number of rationals in [0, 2]
 

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