编号为1,2,3的三个球随意放入编号为1,2,3的三个盒子中,每盒仅放一个球,令Xi 发布时间:2017-02-17 02:45 │ 来源:www.tikuol.com 题型:问答题 问题: 编号为1,2,3的三个球随意放入编号为1,2,3的三个盒子中,每盒仅放一个球,令Xi=(i=1,2),求(X1,X2)联合分布及X1与X2的相关系数.
题型:问答题 —Whom did you ____ the packet at the post office? —Jack. There ____ masses of work for him to do, but he managed to finish the work as required. [ ]A. have fetched; was B. have fetch; were C. have to fetch; were D. have fetch; was 查看答案
题型:问答题 维生素E()A.供试品在碱性条件下水解后,用乙醚萃取,分取乙醚液,加2,2′-联吡啶溶液和三氯化铁溶液,显血红色B.取供试品的氯仿溶液,加25%的三氯化锑氯仿溶液,即显蓝色,渐变为紫红色C.显氯化物的鉴别反应D.显钠盐的鉴别反应E.取供试品溶液,加二氯靛酚钠试液,试液的红色即消失 查看答案