27.Can you still remember the farm we enjoyed plenty of fresh fruit half a year ago?
A.that B.when C.where D.what
26.-What happened to the ancient town?
- .
A.It destroyed in the flood B.The flood was destroying it
C.The flood was destroyed it D.It was destroyed in the flood
25.-Your grandfather is always full of .What’s the secret?
-Playing Taiji every morning.
A.taste B.energy C.relief D.credit
24.--- I am always feeling nervous before an exam.
--- .Do believe your hard work will surely pay off.
A.Take your time B.Take a good rest
C.Take it easy D.Take your turn
23.Although you have traveled to many scenic spots before, of them are as attractive as the one I visited this summer vacation.
A.any B.none C.neither D.all
22.--- I am sorry to have much of your spare time.
--- That’s OK, and I am glad to help you.
A.taken up B.taken on C.taken off D.taken in
第一节:单项填空(共15小题,每小题1分,满分15分)
从A、B、C、D四个选项中,选出可以填入空白处的最佳选项,并在答题卡上将该项涂黑。
21. moment he saw Zhao Benshan’s funny performances, he burs into laughter.
A.A;不填 B.A;the C.The;不填 D.The; a
12.(16分)设数列{an}的前n项和为Sn,
已知a1=1,2Sn=(n+1)an(n∈N*).
(1)求a2,a3,a4的值;
(2)写出从an-1到an的递推公式;
(3)求数列{an}的通项公式.
[解析] (1)由2(1+a2)=3a2,得a2=2.
由2(1+2+a3)=4a3,得a3=3.
由2(1+2+3+a4)=5a4,得a4=4.
(2)∵2Sn=(n+1)an(n∈N*),
∴2Sn-1=nan-1(n>1),
两式相减,得2an=(n+1)an-nan-1,
∴递推公式为an=an-1(n>1).
(3)由(2)得an=an-1
=·an-2
=··an-3
……
=···…··a1=na1.
又∵a1=1,
∴数列{an}的通项公式为an=n(n∈N*).
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