Is There Always a Real Number Between Two Arbitrary Real Numbers?

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Discussion Overview

The discussion revolves around the question of whether there is always a real number between two arbitrary real numbers, focusing on the proof of this statement and the conditions under which it holds. The scope includes mathematical reasoning and proof techniques.

Discussion Character

  • Mathematical reasoning, Debate/contested

Main Points Raised

  • One participant asks for help in proving that for any two arbitrary real numbers x and y, there exists at least one real number z such that x < z < y, suggesting the use of the Archimedean Property.
  • Another participant agrees with the use of the Archimedean Property, indicating a positive response to the initial query.
  • A different participant challenges the initial claim, stating that the assertion is not true as stated unless x and y are distinct, and notes that the requirement for the numbers to be real is unnecessary since the statement also holds for rational numbers and complex numbers.
  • A later reply acknowledges the correction, indicating that the original thought was focused on rational numbers between arbitrary reals.

Areas of Agreement / Disagreement

There is disagreement regarding the initial claim, particularly about the necessity of x and y being distinct and the relevance of the numbers being real. The discussion remains unresolved as participants present differing viewpoints.

Contextual Notes

The discussion highlights limitations regarding the assumptions about the distinctness of x and y and the types of numbers considered (real, rational, complex). These factors influence the validity of the claims made.

courtrigrad
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Hello all

I need help with the following proofs

1. If x and y are arbitrary real numbers, prove that there is at least one real z satisfying x < z < y. (Do I just use the Archimedian Property?)

Thanks
 
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courtrigrad said:
(Do I just use the Archimedian Property?)

Yep. :smile:
 
No. and it isn't true as stated.

x and y must be distinct, and the requirement of being R is unnecessary, since it is true for Q (and C).


what is (x+y)/2?
 
Good catch. I was thinking of rational numbers between arbitrary reals.
 

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