Prove Theorem 5.6 by first determining E(X) and E[X(X + 1)]. Theorem 5.6 The mean and the

Question:

Prove Theorem 5.6 by first determining E(X) and E[X(X + 1)].
Theorem 5.6
The mean and the variance of the negative binomial are
µ = k/θ and σ2 = k/θ(1/θ – 1) Distribution
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