—Of course! Talking with my daughter after the busy work is the greatest joy in my life.
A:loneliness
B:happiness
C:tiredness
(Ⅰ)求证:S3,S9,S6依次成等差数列;
(Ⅱ)a7与a10的等差中项是否是数列{an}中的项?,如果是,是{an}中的第几项?如果不是,请说明理由.
漫画《成功之门》为我们带来的人生启示是 ( )