简答题:
(1)求{an｝的通项公式；
(2)若ak=128，求k．

A 1 B 3 C 2 D 6

A 5m B 1-m C 2m D m+1

A ｛2，4，6，8｝ B ｛2，4｝ C ｛2，4，8｝ D ｛6｝

A 1 B 4 C 2 D <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817183451_5091.png" width="25" height="21" />

A <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817183545_9310.png" width="35" height="41" /> B <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817183549_2435.png" width="59" height="41" /> C <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817183542_2435.png" width="45" height="41" /> D <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817183538_5716.png" width="25" height="42" />

A 2t-3m+1=0 B 2t+3m+1=0 C 2t-3m-1=0 D 2t+3m-1=0