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问题 解答题
若某一等差数列的首项为
C11-2n5n
-
A2n-211-3n
，公差为(
5
2x
-
2
5
3x2
)m展开式中的常数项，其中m是7777-15除以19的余数，则此数列前多少项的和最大？并求出这个最大值．
答案

根据题意，等差数列的首项为C5n11-2n-A11-3n2n-2，

则有

11-2n≤5n
2n-2≤11-3n
，解可得
11
7
≤n≤
13
5
，

又由n∈N，则n=2，

从而有a1=100，

又由7777-15=（76+1）77-15=C7707677+C7717676+C7727675+…+C777676+1-15，

可得m=5，则数列的公差d=-4，

从而等差数列的通项公式是an=104-4n，

设其前k项之和最大，则

104-4k≥0
104-4(k+1)＜0
，

解得k=25或k=26，

故此数列的前25项之和与前26项之和相等且最大，S25=S26=1300．

完形填空

Section B

Hi Colin,

Glad to hear that you are going to have so many adventures in Africa. To make your trip more enjoyable, you should take some necessary things with you. You’ll need strong boots because you are going to  53  a lot.  54  is also necessary in case the weather is bad on Mount Kilimanjaro. A towel is also needed because you will get  55  when you go white-water rafting.

56  very important, too. You must take your tent, sleeping bags and so on. Also take a map of all the places  57  you will visit and a  58  so you don’t get lost. You will take some food and you’ll probably find water. Take care  59 , as you will need to take your water purifying tablets and place them in a pan when you boil the water. And remember to take a pocket knife to cut food or anything else when  60 .

Best wishes,

Jennifer

53. A. run                  B. ride                 C. drive               D. walk

54. A. A parka               B.A raincoat            C. An umbrella         D. A life jacket

55. A. hot                         B. excited              C. wet                D. cold

56. A. An equipment is                              B. Equipments are  

C. Equipment is                              D. The equipments are

57. A. where               B. that                 C. when              D. in which

58. A. compass              B. watch                C. candle                D. box of matches

59. A. although             B. though                     C. however            D. yet

60. A. needed                      B. cut                        C. asked               D. required
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单项选择题 B型题

急性肺水肿

A.双肺满布干啰音

B.局限性湿啰音

C.双肺满布湿啰音

D.两肺底湿啰音

E.局限性干啰音
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