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Math Help - Why is (15 over 4) = to (15 over 11)

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    Why is (15 over 4) = to (15 over 11)

    Why is (15 over 4) = (15 over 11)

    Not division
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    Re: Why is (15 over 4) = to (15 over 11)

    If you're not using "over" to represent division, then what ARE you using it for?
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    Re: Why is (15 over 4) = to (15 over 11)

    It just has in parenthesis 15 over a 4 without a line between them.
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    Re: Why is (15 over 4) = to (15 over 11)

    \left(\begin{array}{c} a \\ b \end{array}\right) is the "binomial coefficient. It is defined as \left(\begin{array}{c}a \\ b \end{array}\right)= \frac{a!}{b!(a- b)!}. So \left(\begin{array}{c} 15 \\ 4\end{array}\right)= \frac{15!}{4! 11!} and \left(\begin{array}{c} 15 \\ 11\end{array}\right)= \frac{15!}{11!4!}. They are the same because 11+ 4= 15.

    (If you really have no idea what the notation means, where did you see this problem?)
    Last edited by HallsofIvy; May 9th 2014 at 05:35 PM.
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    Re: Why is (15 over 4) = to (15 over 11)

    It's on my homework...teacher hasn't taught it to us yet.
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    Re: Why is (15 over 4) = to (15 over 11)

    Quote Originally Posted by IStandAlone99 View Post
    It just has in parenthesis 15 over a 4 without a line between them.
    You are clearly about binomial coefficients.

    $\dbinom{N}{k}=\dfrac{N!}{k!(N-k)!}$ so show that $\dbinom{15}{4}=\dbinom{15}{11}~.$
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