Archimedean property of R proof

In summary, the Archimedean property states that for every real number x, there exists a natural number y such that y>x. To prove the density of Q in R, it is sufficient to show that for any x and y in R, with x<y, there exists a rational number q such that x<q<y. This can be done by considering both negative and positive values for x, and using the definition of a rational number as a fraction of two integers.
  • #1
missavvy
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Homework Statement


Using the density of Q(rationals) in R(real numbers), prove the Archimedean property.


Homework Equations


Density of Q in R: For all x,y in R, and x<y, there exists q in Q s/t x<q<y.
Archimedean property says: For every real number x there exists a natural number y such that y>x.


The Attempt at a Solution


So I know how to prove the density of Q in R using the Archimedean property but I'm not sure of how to do it the other way around. Also, I don't really understand why it makes sense to prove it the other way around? Any hints and explanations would be helpful! thanks
 
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  • #2
The problem does seem that hard. If x is negative y can be 1. If x is positive you know that

x< q < x+1

where q is a positive rational

or
x< q = s/t

Remember what a rational number is ,that is, s and t are integers. You may also have to assume that s and t have no common factors eg we write 3/2 not -3/-2 :-).
 

FAQ: Archimedean property of R proof

1. What is the Archimedean property of R?

The Archimedean property of R states that for any two positive real numbers, there exists a natural number n such that n times the smaller number is greater than the larger number.

2. How is the Archimedean property of R used in proofs?

The Archimedean property of R is often used in proofs to show that a sequence converges to a particular limit. It can also be used to prove the existence of irrational numbers.

3. What is the significance of the Archimedean property of R in mathematics?

The Archimedean property of R is important because it allows us to compare and order any two real numbers. This property is the foundation for many important concepts in calculus and analysis.

4. Can the Archimedean property of R be extended to other number systems?

Yes, the Archimedean property can be extended to other number systems such as the complex numbers, where it states that for any two complex numbers, there exists an integer n such that n times the smaller number is greater than the larger number in terms of absolute value.

5. How was the Archimedean property of R first discovered?

The Archimedean property of R was first discovered by the ancient Greek mathematician Archimedes. He used this property to prove the existence of irrational numbers and to find upper and lower bounds for the value of pi.

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