设二维离散型随机变量 (X,Y) 的分布律为,则( )http://image.zhihuishu.com/zhs/onlineexam/ueditor/201707/4d582c283954479f9e025b8e1f1d75d6.png
举一反三
- X 服从参数为1/9的指数分布，则P｛3 http://image.zhihuishu.com/zhs/onlineexam/ueditor/201707/f0a7e4b429b846099c2e4b240042e6e7.png
- 设p(x.y)为（X,Y）的联合密度函数，则等于（ ）。其中D由 y=2x ，x=1， y=0所围http://image.zhihuishu.com/zhs/onlineexam/ueditor/201707/eca4f0b52ee942efab1fd96aefe6a715.png
- 一维谐振子的哈密顿算符为 。 A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201707/ffe1f4b5eedc462dadafc20bd0daf952.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201707/824bfe9bd226469ba486d5145a62fde4.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201707/c2e73fa49ffd40b38a9fa2c0d0f67f4d.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201707/4364f1f77f4a404ba32a149b075751c9.png" />
- 一质点在平面上作一般曲线运动，其瞬时速度为<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201707/cd2c54e096b2475db8bcecd84e554eb0.png" />，瞬时速率为<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201707/359eb2c648264727bd0a2bc72d54b233.png" />，某一时间内的平均速度为<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201707/32268b5fc5bc43619f3bb1de9c43715b.png" />，平均速率为<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201707/99f1a21b975449648922aab0accdc025.png" />，它们之间的关系必定有（ ）。 A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201707/27daf7237fe740349eb8756c75d23df6.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201707/f2f418f88e564f8c9d46babbe9bc612b.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201707/5d84042638794095a9b9e7760b0cbb53.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201707/cd811196b38f419c82b27356c7d84ca9.png" />
- 设随机变量X的概率密度为[img=212x82]1802f2b4fe7c852.png[/img]令Y = X2，F(x，y)为二维随机变量(X，Y)的分布函数，则F(-1/2, 4) = ( ). A: 1/4 B: 3/4 C: 0 D: 1/8