盒子中装有8个除颜色外完全相同的小球,其中红球5个,黑球3个,若取到红球记2分,取到黑球记1分,现从盒子中任取3个,记总分为![](https://staticzujuan.xkw.com/quesimg/Upload/formula/636c016d552d3ca414d3b1a9d8ed9514.png)
__________ ,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/75c307c420a3546176fbe7fc250252b2.png)
__________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/636c016d552d3ca414d3b1a9d8ed9514.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/75c307c420a3546176fbe7fc250252b2.png)
更新时间:2020-04-27 19:48:54
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【推荐1】已知口袋中装有n(n>1)个红球和2个黄球,从中任取2个球(取到每个球都是等可能的),用随机变量X表示取到黄球的个数,X的分布列如下表所示,则X的数学期望为_________ .
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P | a | b |
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【推荐2】高三(1)班有50名学生,其中30名男生,现从中任选3名学生参加体育抽测,用X表示男生被选中的人数,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8aef464b1f0e9c7e4a33f0741ee1726f.png)
________ ;![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac87b4bd71432d757c7b78bbd6b2dcfd.png)
________ .
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【推荐1】一个箱子里装有大小相同、质地均匀的红球3个、白球2个,从中随机摸出3个球,设摸出红球的个数为
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________ ,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0e60ff3d4d0abd4a75cc521c0267f92e.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b734e8f1546481e3eb4976008a045de.png)
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【推荐2】若一个随机变量的分布列为
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1a83f2ddd3f8fe71e928e3659ca2dd69.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b734e8f1546481e3eb4976008a045de.png)
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