若随机变量
,且
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c90729939d5b8c6f677e13e95e523659.png)
______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1290917c2c835b61384480b335cc1d13.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bc2612fba29976ba74403a197ff19604.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c90729939d5b8c6f677e13e95e523659.png)
更新时间:2020-06-10 19:40:38
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