已知等比数列{a n }中,a 2 ,a 3 ,a 4 分别是某等差数列的第5项、第3项、第2项,且 a 1 = 1 2 公比q≠1. (1)求数列{a n }的通项公式; (2)已知数列{b n }满足bn= log 1 2 a n 2 ,S n 是数列{b n }的前n项和,求证:当n≥5时,a n S n <1.
【简答题】Practice 4-1 Revise the following paragraph. Change the word “nice” into some more interesting words. I had a very nice childhood. I went to a very nice school in Scotland where the teachers were all ...
【单选题】Choose the proper topic sentence for the paragraph. It was a very nice place to live then. Now it is much bigger than before. More people live there and some big businesses opened offices there. My pa...
A.
I lived in a small town when I was a child.
B.
When I have my own children, I want to move to a small town.
C.
The town I live in is very small.
D.
There are two main advantages of living in a small town.