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September 17, 2025, 12:30:35 pm

Author Topic: Chavi's Mathematical adventure (+Karma for solutions)  (Read 15348 times)  Share 

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brightsky

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Re: Chavi's Mathematical adventure (+Karma for solutions)
« Reply #45 on: January 04, 2011, 09:34:03 pm »
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I hate this solution, if you may call it that, but it's probably the fastest way to do Q5:

So sub a = 2x and b = 2y in:
4(x+y)^2 = 50x...[1]
36x^4 + 2y^4 = 41xy^2...[2]

Look at equation [1]:
Since x, y are both positive integers, then 50x must be a multiple of 4, which means x = 2q, where q is some integer.
4(2q + y)^2 = 100q
2q + y = 5sqrt(x)
Again, since q and y are both positive integers, we need x = p^2, where p is some integer.
So we have 2q = p^2
The only solution here (besides 0) is q = 2 and p = 2, which means x = 4, which in turn means that y = 6.
« Last Edit: January 04, 2011, 09:41:23 pm by brightsky »
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pi

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Re: Chavi's Mathematical adventure (+Karma for solutions)
« Reply #46 on: January 04, 2011, 10:14:07 pm »
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That brilliant!

Thanks brightsky (+1 karma well deserved there)

pi

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Re: Chavi's Mathematical adventure (+Karma for solutions)
« Reply #47 on: January 05, 2011, 12:41:22 pm »
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I think this is what you meant brightky (you got x=4, which would make a=8... which is incorrect - would also make b = 12)



Using



As and ,
As , let
As , let

or
As ,





Still have no idea on question 6...
« Last Edit: January 05, 2011, 01:15:00 pm by Rohitpi »