题目 若随机变量X的分布列为 (X=k)=dfrac (c)(k(k+1)) ,k=1,-|||-2,3,4,其中c为常数,则 (dfrac (1)(2)lt Xlt dfrac (5)(2)) 的值为-|||-()-|||-A. dfrac (4)(5) B. dfrac (5)(6)-|||-C. dfrac (2)(3) D. dfrac (3)(4) 题目解答答案