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   Author  Topic: Difference of powers  (Read 443 times)
NickH
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Difference of powers  
« on: May 1st, 2003, 3:18pm »
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Find all ordered pairs (m,n) of positive integers such that |3m - 2n| < 10.
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Leo Broukhis
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Re: Difference of powers  
« Reply #1 on: Jul 8th, 2003, 9:14am »
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(1,2)
(2,1)
(2,2)
(1,3)
(2,3)
(2,4)
(3,5)
 
What did I miss?
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towr
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Re: Difference of powers  
« Reply #2 on: Jul 8th, 2003, 9:55am »
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on Jul 8th, 2003, 9:14am, Leonid Broukhis wrote:

What did I miss?

(1,1)
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Leo Broukhis
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Re: Difference of powers  
« Reply #3 on: Jul 8th, 2003, 10:30am »
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That was a stupid mistake: I started listing pairs from (0,0),
then realised that m and n must be positive, and cut a group of lines that contained 0. (1,1) must have been somewhere among them. But really, why is it medium? Because of (3,5)? Or because you need to prove that there are no more? Well, continuous fractions of log(3)/log(2) help to do that.
« Last Edit: Jul 8th, 2003, 10:31am by Leo Broukhis » IP Logged
NickH
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Re: Difference of powers  
« Reply #4 on: Jul 9th, 2003, 12:45pm »
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I placed it in medium because of the need to prove there are no more.
 
Please could you expand on the continued (?) fractions technique?
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Leo Broukhis
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Re: Difference of powers  
« Reply #5 on: Jul 9th, 2003, 5:21pm »
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After some thought, maybe it doesn't help to prove that there are no more, only to make me convinced about it. Smiley
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