若等差数列{a n }的首a 1 ,公差为d,前n项的和为S n ,则数列{ S n n }为等差数列,且通 S n n =a 1 +(n-1) d 2 .类似地,请完成下列命题:若各项均为正数的等比数列{b n }的首b 1 ,公比为q,前n项的积为T n ,则数列______为等比数列且通______.
【简答题】Unit 1 News1(1).mp3 按以下结构完成新闻听力的结构分析 Topic sentence: ______________. Two findings: (1)_______________ a. _______________ b. _______________ (2)_______________ a. _______________ b. _______________