Proving m + 1/m = Integer When m = 1

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SUMMARY

The discussion centers on proving that if m is a positive rational number, then m + 1/m is an integer only when m = 1. Participants clarify that m can be expressed as p/q, where p and q are natural numbers. They conclude that for the expression p/q + q/p to yield an integer, both p must divide q and q must divide p, leading to the only solution being when m equals 1. The conversation emphasizes the importance of understanding coprime integers and the implications of prime factors in this proof.

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  • #31
I showed that my premise, that there is a lowest terms fraction satisfying a/b+b/a=n leads to the conclusion that fraction is, in fact, not in lowest terms. This is an impossible situation. Hence I must have been wrong in assuming such a fraction exists.
 
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  • #32
I think the initial assumption that \frac {a}{b} is in the lowest terms, hence they are co-prime (or rather no common factors), but you've proven that there exists a prime factor p that divides both of them, hence they are not co-prime which is a contradiction.

Anyway why do we even use co-prime when "no common factor" suffices?

EDIT: I can't seem to get the latex to work :(
 
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  • #33
I usually say relatively prime when "no common factor" suffices. Just force of habit, I guess.
 
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  • #34
What is RHS? You mentioned it in your proof.
 
  • #35
RHS='right hand side' (of the equation).
 

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