Let X∼Binomial(n,p)X \sim \text{Binomial}(n, p)X∼Binomial(n,p). Find the expected value of X(X−1)X(X-1)X(X−1).
n(n−1)p2n(n-1)p^2n(n−1)p2
n2p2n^2 p^2n2p2
n(n−1)p(1−p)n(n-1)p(1-p)n(n−1)p(1−p)
n p^2