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Thread: closed under subtraction

  1. April 11th 2010, 11:48 PM #1
    alyssams
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    closed under subtraction

    how do i prove that for any a,b in Z, the set L sub(a,b) is closed under subtraction
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  2. April 12th 2010, 01:49 AM #2
    tonio
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    Quote Originally Posted by alyssams View Post
    how do i prove that for any a,b in Z, the set L sub(a,b) is closed under subtraction

    It'd be a very good idea if you'd tell what in the world is Lsub(a,b)...

    Tonio
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  3. April 12th 2010, 06:22 AM #3
    alyssams
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    sorry, La,b is (ax+by:x,y element of Z)
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  4. April 12th 2010, 06:34 AM #4
    maddas
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    (ax+by)-(ax'+by') = a(x-x')+b(y-y)'\in L_{a,b}?
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