搜题请搜索小程序“爱下问搜题”
问题 选择题
若（5+4x）n的展开式中各项二项式系数之和为an，（3x2+9
x
）n的展开式中各项系数之和为bn，则
bn
an
的值为（　　）
A．2nB．3nC．24nD．6n
答案

由题意可得，an=Cn0+Cn1+…+Cnn=2n

设（3x2+9

x
）n=a0+a1x+…+anx2n

令x=1可得各项系数之和为bn=12n

∴

bn
an
=
12n
2n
=6n

故选：D

阅读理解
阅读下面短文,掌握其大意,从A、B、C、D四个选项中选出最佳选项.
                                               Articles Wanted
                                               School Life
▲Articles should be typewritten (打印的) and double spaced, using only one side of the page.
▲Your name, year of birth, school name (and English teacher), home address and e-mail address must be
included.
▲For photos, place the information on the back of each envelope: PLEASE DON'T FOLD.
▲Please keep copies of your text, pictures or photos.
▲The sentence MUST BE WRITTEN with your name on each work, "I promise the above work is
completely original (原创的)."
▲If your article is chosen, you will receive a copy of School Life and a special gift.
                           SEND IT ALL SUMMER!
For more information, please contact us!
Tel: (02) 92136116     (02) 92674363
E-mail: schoollife@acpmagazines.com.au
Mail: School Life. Box 5252, Sydney, NSW 200
                        
1. According to the passage, you can send your articles_________.
A. within 3 weeks  
B. all summer  
C. all the year round  
D. during the whole term
1. How many ways can you find in the passage to contact School Life?  
A. 1.            
B. 2.            
C. 3.            
D. 4.
3. The underline word "FOLD" means __________.     
A. 折叠;对折    
B. 包;笼罩      
C. 抱住    
D. 交叉;合拢
4. Who do you think will write articles for School Life?    
A. Students who are interested in writing.    
B. Teachers who love writing and taking photos.
C. Parents who wish their kids to be popular writers.  
D. Readers who had a happy time in their childhood.
查看答案
判断题

大风天气行车中，如果遇到狂风袭来，感觉机动车产生横向偏移时，要急转方向以恢复行驶方向。
查看答案