和等差数列一样 ,等比数列也是高中代数中的基本问题 .等比数列包括项数n ,首项a1,通项an,公比 q和前n项和Sn 这五个基本元素 ,它们之间满足an=a1qn- 1和Sn=a1(1- qn)1- q 两个关系式 ,只要知道其中任意三个元素 ,便可以求出其它两个元素 .学习数列要注意培养熟练地求出其中任 Like the arithmetic sequence, the geometric sequence is a basic problem in the high school algebra. The geometric sequence includes the number n, the first term a1, the general term an, the common ratio q, the first n terms, and the Sn basic elements. Between the two expressions an=a1qn-1 and Sn=a1(1-qn)1-q, the two other elements can be found as long as any three elements are known. The learning sequence must be trained carefully Among them