Can You Prove There Are Infinite Rationals Between Two Real Numbers?

[Shing]

Homework Statement

If x and y are arbitrary real numbers. x>y. prove that there exist at least one rational number r satisfying x<r<y, and hence infinitely.

The Attempt at a Solution

well, I have done my proof, but comparing to the solution offered by http://ocw.mit.edu/NR/rdonlyres/Mathematics/18-014Calculus-with-Theory-IFall2002/1C8FA521-FDCE-491B-8689-955B04A4A4A2/0/pset2solutions.pdf" (*1), I have a bit doubt about whether my proof is precise enough or not.

anyway, here it is:

x,y belong to R, x<y
let|x-y|&gt;\varepsilon
let n belongs Z, n>1
obviously,\varepsilon satisfies x&lt;x+\frac{\varepsilon}{n}&lt;y
as there exist infinite numbers for n,
therefore, infinite r satisfy x<r<y

thanks for reading =)

 

[rs1n]

Homework Statement

If x and y are arbitrary real numbers. x>y. prove that there exist at least one rational number r satisfying x<r<y, and hence infinitely.

The Attempt at a Solution

well, I have done my proof, but comparing to the solution offered by http://ocw.mit.edu/NR/rdonlyres/Mathematics/18-014Calculus-with-Theory-IFall2002/1C8FA521-FDCE-491B-8689-955B04A4A4A2/0/pset2solutions.pdf" (*1), I have a bit doubt about whether my proof is precise enough or not.

anyway, here it is:

x,y belong to R, x<y
let|x-y|&gt;\varepsilon
let n belongs Z, n>1
obviously,\varepsilon satisfies x&lt;x+\frac{\varepsilon}{n}&lt;y
as there exist infinite numbers for n,
therefore, infinite r satisfy x<r<y

thanks for reading =)

If \epsilon is not a rational number, then is \epsilon/n rational?

If |x-y|&gt;\epsilon then can you find a rational number such that \epsilon is larger than this rational number? The rest of your arguments can be used provided you find this rational number.