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Math Help - inf proof question..

  1. #1
    MHF Contributor
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    inf proof question..

    its given that "x" is a low bound of non empty group A.
    prove that x=inf A for e>0 there is "y" which x<=y<=x+e
    ??

    i cant understand this question

    i know how to prove that a certain number is inf or sup using only the formula of the group

    but here i dont have the formula of the geoup
    and i have this 'y' i dont know why its for??
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  2. #2
    MHF Contributor
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    i think i got it
    A bounded from the bottom
    x is a low bound of A

    i need to prove that x=inf A


    this expression is just the definition of inf
    x<=y<=x+e


    so i tried to solve it as if i got a formula
    I presume that "x" is not inf
    then our inf is x+e
    now i proove that x+e is not infA
    x+e>y

    but here i got stuck because in this step i would do a formula operation.

    ??
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