已知函数f（x）=㏒_ax（a＞0且a≠1），若数列2，f（a₁），f（a₂），…，f（a_n），2n+4（n∈N^*）成等差数列

（1）求数列{a _n}的通项a _n；

（2）令b _n=a_nf（a_n），当a＞1时，判断数列{b_n}的单调性并证明你的结论．

词汇运用（每题1分, 共计10分）

A. 用括号内所给单词的适当形式完成句子

小题1:He is            (funny) than his twin brother.

小题2:It         (take) my sister about 20 minutes to get to school yesterday.

小题3:Don’t         (担心) about me. I’m OK now.

小题4:There are many           (河流) and lakes in our hometown.

小题5:My favorite subject is          (化学) .

B. 选择正确词组填空 (必须写序号)

小题6:Can you              to my house to discuss the science report?

小题7:What do you               the transportation in Huzhou?

小题8:          watching TV, only a few students watch TV every day..

小题9:Eating a balanced diet is a good way to           .

小题10:You should lie down and             .