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Math Help - Show that for all integers r,s

  1. #1
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    Show that for all integers r,s

    Quite straightforward, but it's proving somewhat frustrating for me.

    Show that for all integers r,s with 2(r^2)+1= s, one of r and s must be divisble by 3.
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  2. #2
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    Quote Originally Posted by Jamot69 View Post
    Quite straightforward, but it's proving somewhat frustrating for me.

    Show that for all integers r,s with 2(r^2)+1= s, one of r and s must be divisble by 3.
    If r has form 3k+1 then 2(r^2)+1 is divisible by 3, so s is divisible by 3. If r has form 3k+2 the same idea applies. Otherwise r has form 3k but then there is nothing to show.
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