设则＝（ ） 。https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/30c573e7ca79488fb1ae28beed5356e9.png
举一反三
- 设随机变量X~N(4,2)，则其特征函数为(). A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/357ad388efa144a1a2b824e2b1ded239.png" > B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/d52e72841a81484981168cbb693bad24.png" > C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/00e1e0c2bba04889b58eb483c88821fb.png" > D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/1851c30670244a5c821128d6c44a3ecc.png" >
- 下列逻辑命题正确的是（）。 A: 若Y=A+B则<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/2ac821feb3d7451a8c7c69c97de1ca39.png">=<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/d900fde7b3dc4b2ea24859c0712ddd0c.png"> B: 若A+B=A+C则B=C C: 若Y=A+B则<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/e305d54dd8c94adfaf570a2f0e6d4421.png">=<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/3cb33b429abf4ec397173f58dcdd37af.png">+<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/87aa5698238b4b66b9264426769b7b17.png"> D: 若AB=AC则B=C
- 从数字<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/2d61a913ea754ceab9283348404e99b8.png" >中任取两个不同的数字，则这两个数字之差的绝对值的数学期望为()。 A: 1 B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/7da33d3a3bd54a188acf94dfdbab4f56.png" > C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/e8d44a97a0d141198c56ce68511897c9.png" > D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/fa3d4d77c7ea4487a9fd484134badc5e.png" >
- 为使锅垢中难溶于酸的CaSO4转化为易溶于酸的CaCO3，常用Na2CO3处理，反应式为CaSO4+CO32-<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/88320eab77594b6abf0039ab0efe3c57.png" />CaCO3+SO42-，此反应的标准平衡常数为（）。 A: K<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/e8c371ce6b96487e829331bb8dee134f.png" />(CaSO4)·K<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/e8c371ce6b96487e829331bb8dee134f.png" />(CaCO3) B: K<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/e8c371ce6b96487e829331bb8dee134f.png" />(CaCO3)/K<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/e8c371ce6b96487e829331bb8dee134f.png" />(CaSO4) C: [K<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/e8c371ce6b96487e829331bb8dee134f.png" />(CaSO4)·K<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/e8c371ce6b96487e829331bb8dee134f.png" />(CaCO3)]1/2 D: K<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/e8c371ce6b96487e829331bb8dee134f.png" />(CaSO4)/K<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/e8c371ce6b96487e829331bb8dee134f.png" />(CaCO3)
- 10人中至少有2人同生日的概率是多少？（1年按365天计算）() A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/f3b577db2dd0429b9eab51dff5644b23.png" > B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/6f30552128e14bfb89b26b30ac2b72db.png" > C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/fa8f9ba9bd2d4a40b7d007fd9e9988fd.png" > D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/201911/05a12b5d4da04e2c9ea779b313981c83.png" >