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Subject: "elementary number theory problem"     Previous Topic | Next Topic
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gkvp
Member since Jan-1-08
Feb-26-08, 08:44 PM (EST)
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"elementary number theory problem"
 
   Let P and Q be two different odd natural numbers, with P<Q.
Let L(N) be the set of odd natural numbers less than or equal to N.
Let L(Q)\L(P) denote those integers in L(Q) but not in L(P).

Prove that the sum of all integers in L(P) never equals the sum of all integers in L(Q)\L(P).


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alexbadmin
Charter Member
2192 posts
Feb-26-08, 08:55 PM (EST)
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1. "RE: elementary number theory problem"
In response to message #0
 
   Let S(P) be the sum of all the numbers in L(P).

It's known that S(2n-1) = n².

The sum of numbers in L(Q)\L(P) is S(Q) - S(P). If

S(Q) - S(P) = S(P)

then

S(Q) = 2S(P)

which can't be because on the left there is a square of an integer whilst on the right the number is not a square unless sqrt(2) is rational.


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