Zoe,your current colleagues,is leaving for a new position at a different company.Write a letter to congratulale her on the new job.You should write about 100 words neatly on the ANSWER SHEET.Do not sign your own name.Use"Li Ming"instead.Do not write your address.
Dear Zoe,
I was thrilled to hear about your new job in the ABC Company.I know it's been a long search to find the right position,but it seems this is going to be a good match for your skills and experience.I'm sad to see you go and certainly will nuss our Monday morrung tea breaks.However,I feel certain that you're making the right choice by accepting dus position.This is such a wonderful opportunity for you and I'm sure you'II do a fantastic job over there.Best luck for vour days in the new position.Refards,
Li Ming
设随机变量X,y独立同分布,且X～N（0,σ^2）,再设U=aX+by,V=aX-bY,其中a,b为不相等的常数.求：
(1)E(U),E(V),D(U),D(V),
;
(2)设U,V不相关,求常数A,B之间的关系.
设A，B为随机事件，且
求：(Ⅰ)二维随机变量(X，Y)的概率分布；
(Ⅱ)X与Y的相关系数ρXY.
设有来自三个地区的各10名、15名和25名考生的报名表,其中女生的报名表分别为3份、7份和5份,随机取出一个地区,再从中抽取两份报名表.
(1)求先抽到的一份报名表是女生表的概率p;
(2)设后抽到的一份报名表为男生的报名表,求先抽到的报名表为女生报名表的概率q.
设二维随机变量(X，Y)服从区域G上的均匀分布，其中G是由x-y=0，x+y=2，与y=0所围成的三角形区域.
(Ⅰ)求X的概率密度fx(x)；
(Ⅱ)求条件概率密度.
设X1,2X,…,Xn（n>2）相互独立且都服从N(0,1),Yi=Xi-X（i=1,2,…,n）.求：
(1)D(Yi)(i=1,2,…,n);(2)Cov(Y1,Yn);(3)P(Yn+Yn≤0).
设(X,Y)的联合密度函数为f(x,y)=
(1)求a；(2)求X,Y的边缘密度,并判断其独立性；(3)求.
已知甲、乙两箱中装有同种产品，其中甲箱中装有3件合格品和3件次品，乙箱中仅装有3件合格品.从甲箱中任取3件产品放入乙箱后，求：
(1)乙箱中次品件数X的数学期望；
(2)从乙箱中任取一件产品是次品的概率.
