Duty is an act or a course of action that people ______you to take by social customs, law or religion.

Project（71）is an uncertain event or condition that，if it occurs，has a positive or a negative effect on at least one project objective，such as time，cost，scope，or quality．

Project ______is an uncertain event or condition that，if it occurs，has a positive or a negative effect on at least one project objective，such as time，cost，scope，or quality．

● Project（71）is an uncertain event or condition that, if it occurs, has a positive or a negative effect on at least one project objective, such as time, cost, scope, or quality.（71）

已知等比数列{an}的公比为2，S4＝1，则S8＝（　　）．

数列{an}是公差不为0的等差数列，且a1，a3，a7为等比数列{bn}的连续三项，则数列{bn}的公比为（　　）．

在等比数列{an}中：　　（1）已知，求；　　（2）已知；　　（3）已知，求与；　　（4）已知

已知数列{an}的通项公式为an =(4 9) n-1 - (2 3) n-1 (n ∈ N∗ ),则数列{an}( ).

Do you like an apple or a banana?（）

根据军队建设的需要，军队院校可以从青年学生中招收（）。

已知a1=3且an=Sn-1+2n，求an及AN。

已知a、6都是正数，X(a²+1)(b²+4)=8ab，则a +b/2的值为(    )。