Variance of Discrete Random Variable from PGF/Motivation

Variance of Discrete Random Variable from PGF: Also known as

Variance of Discrete Random Variable from PGF shows how to find the variance of a discrete random variable without the need to go through the tedious process of what might be a complicated and fiddly summation.

All you need to do is differentiate its PGF twice, and plug in $1$.

Assuming, of course, you know what its PGF is.

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