题目
题型:汕头二模难度:来源:
7 |
10 |
(1)请你判断该班文娱小组的人数并说明理由;
(2)求ξ的分布列与数学期望.
答案
(1)∵P(ξ>0)=1-P(ξ=0)=
7 |
10 |
3 |
10 |
| ||
|
3 |
10 |
∴
(7-2x)(6-2x) |
(7-x)(6-x) |
3 |
10 |
∴x=2,
∴7-x=5
故文娱队共有5人.
(2)P(ξ=0)=
3 |
10 |
| ||||
|
3 |
5 |
| ||
|
1 |
10 |
ξ的分布列为:
7 |
10 |
7 |
10 |
3 |
10 |
| ||
|
3 |
10 |
(7-2x)(6-2x) |
(7-x)(6-x) |
3 |
10 |
3 |
10 |
| ||||
|
3 |
5 |
| ||
|
1 |
10 |