方差在任何情况下都是正数，协方差值可正可负。
摩擦学面临挑战
Your company has a main office and one branch office. All servers run Windows Server 2003 Service Pack 2 (SP2). The relevant portion of the network is configured as shown in the exhibit. (Click the Exhibit button.) All computers in the branch office are configured to use DNS2 as their DNS server.Users in the branch office report that they cannot resolve the IP addresses for servers on the Internet. You run Dnscmd as shown in the following Command Prompt window.You need to ensure that users in the branch office can resolve the names of Internet hosts. What should you do on DNS2?（） ["Remove the root zone. ","Clear the DNS server cache. ","Configure the contoso.com zone as a primary zone. ","Configure the adatum.com zone as a secondary zone and DNS1 as the master DNS server."]
证券组合相对于自身的β值就是1。
发现有人在低压设备上触电，当触电人离电源开关近时，应怎样使触电者脱离电源？
制定和实施资本充足率的作用主要体现在哪几方面？
