(Mean square of a geometric random variable) Let x Geom(p) and q = 1-p. Derive the formula To compute this conveniently,start with Hint. E(X2)=E(X)+Elx(X-1), Then note that in the geometric ELX(X - 1)] can be computed with the derivative technique of but with the second derivative because ry" k(k 1)*2 for k2 2.