[题目]一高速运动电子的总能量为其静能的-|||-倍,则电子的速度为 ()-|||-A、kC-|||-B、 dfrac (c)(k)-|||-C、 dfrac (c)(k)sqrt (1-{k)^2}-|||-D、 dfrac (c)(k)sqrt ({k)^2-1}

根据sigma =dfrac ({K)_(1C)}(sqrt {pi C)},如sigma =dfrac ({K)_(1C)}(sqrt {pi C)}瓷的si

X=k =dfrac (c)(k!) ,=0, 1,2,3...... X=k =dfrac (c)(k!) ,=0, 1,2,3...... X=k =dfr

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

)-|||-B .(X=k)=dfrac (1)({3)^k}(k=1,2,... )-|||-C .(X=k)=dfrac (1)({3)^k}(k=0,1

) ( )-|||-(A) =pm (2k+1) (B) =pm 2k-|||-(C) =pm dfrac (1)(2)(2k+1) (D) =pm dfrac

2.5 已知离散型随机变量X的分布律为 X=k =(p)^k+1(k=0,1), 则 p= ()-|||-(A) dfrac (sqrt {5)-1}(2)

设随机变量X的分布律为 (X=k)=dfrac (C)(k!)! ,k-|||-=0 ,1,2,...,则 ((X)^2)= __ :

(3)设随机变量X的分布律为 X=k =dfrac (c)(k!)! , k=0 ,1,2,···,则 ((X)^2)= __ .

(6)设随机变量X的分布律为 X=k =dfrac (c)(k!)(e)^-2 .=0,1,2, ···,则常数 c= __ .

设随机变量X的概率分布为 X=k =dfrac (c)(n)cdot k ,k=1,2 ,···,n,则常数 = __-|||-