If X∼Geometric(p)X \sim Geometric(p)X∼Geometric(p), where XXX is the number of trials until the first success, what is E[X2]E[X^2]E[X2]?
(2−p)/p2(2-p)/p^2(2−p)/p2
(1−p)/p2(1-p)/p^2(1−p)/p2
(2−p)/p(2-p)/p(2−p)/p
1/p21/p^21/p2