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Math Help - [SOLVED] Probability (probability mass function,pmf)

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    [SOLVED] Probability (probability mass function,pmf)

    If X has the probability mass function f(x) = k / x! (x=0,1,2,...),
    what is the value of k?
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    Quote Originally Posted by nameck View Post
    If X has the probability mass function f(x) = k / x! (x=0,1,2,...),
    what is the value of k?
    You must have \sum_{x=0}^\infty \frac{k}{x!}= k\sum_{x=0}^\infty \frac{1}{x!}= 1.
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    how to cancel the factorial(!) sign?
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    Quote Originally Posted by nameck View Post
    how to cancel the factorial(!) sign?
    At this level you are expected to know that \sum\limits_{x = 0}^\infty  {\frac{1}{{x!}}}  = e.
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