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