数列{an}中,前三项依次为1/(x+1),5/(6x),1/x.则a101等于?
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/19 09:20:12
![数列{an}中,前三项依次为1/(x+1),5/(6x),1/x.则a101等于?](/uploads/image/z/766745-17-5.jpg?t=%E6%95%B0%E5%88%97%7Ban%7D%E4%B8%AD%2C%E5%89%8D%E4%B8%89%E9%A1%B9%E4%BE%9D%E6%AC%A1%E4%B8%BA1%2F%EF%BC%88x%2B1%EF%BC%89%2C5%2F%EF%BC%886x%EF%BC%89%2C1%2Fx.%E5%88%99a101%E7%AD%89%E4%BA%8E%3F)
数列{an}中,前三项依次为1/(x+1),5/(6x),1/x.则a101等于?
数列{an}中,前三项依次为1/(x+1),5/(6x),1/x.则a101等于?
数列{an}中,前三项依次为1/(x+1),5/(6x),1/x.则a101等于?
如果是等比数列,利用等比中项列方程
1/(x + 1) 1/x = (5/(6 x))^2
可解得x = 25/11
a1 = 11/36 q = 6/5
a101 = 11/36 (6/5)^100
如果是等差数列,利用等差中项列方程
x = 2
a1 = 1/3 ,d = 1/12
a101 = 1/3 + 100 1/12 = 26/3