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Math Help - Prooving Factors

  1. #1
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    Prooving Factors

    How would I prove that 4 is a factor of 6a x 10b ?
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  2. #2
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    Re: Prooving Factors

    Quote Originally Posted by calmo11 View Post
    How would I prove that 4 is a factor of 6a x 10b ?
    is 4 a factor of 60?
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  3. #3
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    Re: Prooving Factors

    Yes, how does that relate to the above?
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  4. #4
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    Re: Prooving Factors

    Is it like you say 6a x 10b = 4t
    60ab=4t
    4(15ab)=4t
    If 15ab is an integer
    Then let 15ab=t
    4t=4t ?
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  5. #5
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    Re: Prooving Factors

    Assuming $a, b \in \mathbb{Z}$

    $\dfrac{6a \times 10b}{4}=\dfrac{60ab}{4}=15ab \in \mathbb{Z}$

    The last statement by closure of multiplication over the integers.

    and so $4 \times 15ab = 6a \times 10b$ and 4 is thus a factor of $6a \times 10b$

    That's really all there is to it.
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