1. Joined
    25 Aug '06
    Moves
    0
    12 Feb '07 02:20
    True or false:

    if a, b, c and d are positive integers, and ab=cd, then a+b+c+d cannot be a prime number.
  2. Standard membercelticcountry
    Copyright ©2001-2006
    Eastbourne
    Joined
    20 Sep '04
    Moves
    16434
    12 Feb '07 13:12
    Originally posted by David113
    True or false:

    if a, b, c and d are positive integers, and ab=cd, then a+b+c+d cannot be a prime number.
    unproveable.

    so false.
  3. Standard memberXanthosNZ
    Cancerous Bus Crash
    p^2.sin(phi)
    Joined
    06 Sep '04
    Moves
    25076
    12 Feb '07 13:32
    Originally posted by celticcountry
    unproveable.

    so false.
    If you wish to state that it is unprovable you need to prove that this is the case.
    And even if it is unprovable that doesn't mean it's false unless a counter example exists.
  4. Standard membercelticcountry
    Copyright ©2001-2006
    Eastbourne
    Joined
    20 Sep '04
    Moves
    16434
    12 Feb '07 13:59
    Originally posted by XanthosNZ
    If you wish to state that it is unprovable you need to prove that this is the case.
    And even if it is unprovable that doesn't mean it's false unless a counter example exists.
    if youy cant proove something, it is assumed false.

    not all primes are known. so there is no proof.
  5. Standard memberXanthosNZ
    Cancerous Bus Crash
    p^2.sin(phi)
    Joined
    06 Sep '04
    Moves
    25076
    12 Feb '07 14:00
    Originally posted by celticcountry
    if youy cant proove something, it is assumed false.

    not all primes are known. so there is no proof.
    You're an idiot.
  6. Joined
    30 Oct '04
    Moves
    7797
    12 Feb '07 14:43
    Let's try this:
    If ab=cd, then there exist integers x,y, z and t such that:
    a=xz, b=yt, c=xt, d=yz. (one or more of these integers may be equal to 1).
    Then a+b+c+d = xz+yt+xt+yz = x(z+t) + y(z+t) = (x+y)(z+t) which consists of two different integers, hence can never be a prime. Does that sound right?
  7. Joined
    07 Sep '05
    Moves
    35068
    12 Feb '07 16:001 edit
    Originally posted by celticcountry
    if youy cant proove something, it is assumed false.
    If you can't prove something, you assume nothing. Welcome to mathematics.

    There are a few conjectures out there that people think are probably true, but we can't prove. Fermat's Last Theorem used to be an example.


    (Even if you can prove it's unproveable, you're still on shaky ground assuming it's false).
  8. Account suspended
    Joined
    18 Mar '06
    Moves
    3118
    12 Feb '07 17:07
    Originally posted by XanthosNZ
    You're an idiot.
    agreed
  9. Joined
    21 Feb '06
    Moves
    6830
    12 Feb '07 17:11
    Originally posted by ilywrin
    Let's try this:
    If ab=cd, then there exist integers x,y, z and t such that:
    a=xz, b=yt, c=xt, d=yz. (one or more of these integers may be equal to 1).
    Then a+b+c+d = xz+yt+xt+yz = x(z+t) + y(z+t) = (x+y)(z+t) which consists of two different integers, hence can never be a prime. Does that sound right?
    Maybe I'm being stupid, but why is this true?

    If ab=cd, then there exist integers x,y, z and t such that:
    a=xz, b=yt, c=xt, d=yz. (one or more of these integers may be equal to 1).
  10. Joined
    11 Nov '05
    Moves
    43938
    12 Feb '07 17:21
    Originally posted by XanthosNZ
    You're an idiot.
    Showing once more your complete lack of social competence...
  11. Standard memberXanthosNZ
    Cancerous Bus Crash
    p^2.sin(phi)
    Joined
    06 Sep '04
    Moves
    25076
    12 Feb '07 17:23
    Originally posted by FabianFnas
    Showing once more your complete lack of social competence...
    You are also an idiot.
  12. Joined
    11 Nov '05
    Moves
    43938
    12 Feb '07 17:49
    Originally posted by XanthosNZ
    You are also an idiot.
    And you are the only one in the whole world who is not an idiot?
    How lonely you must feel...

    I don't mind you calling me an idiot, I know you too good for that.
    But an apology to celticcountry would be appropriate.
  13. Standard memberXanthosNZ
    Cancerous Bus Crash
    p^2.sin(phi)
    Joined
    06 Sep '04
    Moves
    25076
    12 Feb '07 17:58
    Originally posted by FabianFnas
    And you are the only one in the whole world who is not an idiot?
    How lonely you must feel...

    I don't mind you calling me an idiot, I know you too good for that.
    But an apology to celticcountry would be appropriate.
    celticcountry can go suck eggs. His posts in this thread earned him the title of idiot, did you read them?
  14. Joined
    07 Sep '05
    Moves
    35068
    12 Feb '07 18:09
    Originally posted by Fat Lady
    Maybe I'm being stupid, but why is this true?

    If ab=cd, then there exist integers x,y, z and t such that:
    a=xz, b=yt, c=xt, d=yz. (one or more of these integers may be equal to 1).
    That was my first thought. On second thought I think it is true, but it isn't obvious.

    If you define x as the product of the prime factors of a that it shared with c, and y as the product of the prime factors of b that it shares with d...

    ...and then you can define z and t by a = xz and b = yt...

    ...then I think that you can show that c = xt and d = yz. But I haven't worked it through fully yet.
  15. Joined
    11 Nov '05
    Moves
    43938
    12 Feb '07 18:561 edit
    Originally posted by XanthosNZ
    celticcountry can go suck eggs. His posts in this thread earned him the title of idiot, did you read them?
    Yes, I did, and he is cleverer than the most people of this earth.

    You didn't like when I call you social incompetent, do you think he likes to be called an idiot? This is the flaw in your personality that I call lack of emotional competence.

    Now you force me to show for everybody your lack of social competence and lack of emotional competence.

    How does it feel to be without both social and emotional competence?

    Now, now, just say "I apologize, I was stupid to say that" to celticcountry? Just to show that I am wrong in the personality analyze of you?
Back to Top