数列{an}满足a1=2,a2=5,an+2=3an+1-2an. (1)求证:

题型:解答题

问题:

数列{an}满足a1=2,a2=5,an+2=3an+1-2an

(1)求证:数列{an+1-an}是等比数列;

(2)求数列{an}的通项公式;

(3)求数列{an}的前n项和Sn

考点:等比数列的通项公式等比数列的前n项和
题型:解答题
Everyone needs friends. We all like to        close to someone. It is nice to have a friend to talk, laugh and do things with.       , sometimes we need to be alone. We don’t always want people       . But we would feel lonely if we never had a friend.
No two people are       . Friends sometimes don’t get on well. That doesn’t mean       they no longer like each other. Most of the time they will make up(言归于好),and become       again.
Sometimes friends move away. Then we feel very       . We miss them very much, but we can        them and write to them. It could be possible that we could even see them again. And we can also       new friends.
There’s more good news for people who have friends. They live longer than people who don’t have. Why? It could be that they are       . Being happy helps you stay well and it could be good just knowing that someone cares about you.
小题1:
A.lookB.watchC.feelD.see
小题2:
A.HardlyB.NearlyC.SuddenlyD.Certainly
小题3:
A.aloneB.awayC.all overD.around
小题4:
A.friendlyB.kindC.just the sameD.quite different
小题5:
A.thatB.whetherC.howD.why
小题6:
A.enemiesB.strangersC.studentsD.friends
小题7:
A.angryB.sadC.happyD.alone
小题8:
A.callB.askC.tellD.talk with
小题9:
A.look forB.findC.makeD.know
小题10:
A.happierB.strongerC.kinderD.richer
题型:解答题

下列属于生态系统的是(  )

A.泰山林区

B.草原中所有的牛、羊

C.大明湖中的所有生物

D.黄河中所有的鱼

题型:解答题

喷灯在加油,放油或维护修理时必须灭火,卸压,冷却后方可进行。

题型:解答题

患者,女,45岁。失眠2个月,近日来入睡困难,有时睡后易醒,醒后不能再睡,甚至彻夜不眠,舌苔薄,脉沉细。治疗应首选

A.神门、内关
B.神门、胆俞
C.申脉、照海
D.心俞、脾俞
E.心俞、足三里

题型:解答题

毡呢(由化纤制作,未浸渍、涂布、包覆或层压)

更多题库