问题 填空题

若实数a,b,c满足2a+2b=2a+b,2a+2b+2c=2a+b+c,则c的最大值是______.

答案

由基本不等式得2a+2b2

2a2b
=2×2
a+b
2
,即2a+b2
2a2b
=2×2
a+b
2
,所以2a+b≥4,

令t=2a+b,由2a+2b+2c=2a+b+c可得2a+b+2c=2a+b2c,所以2c=

t
t-1
=1+
1
t-1

因为t≥4,所以1<

t
t-1
4
3
,即1<2c
4
3
,所以0<c≤log2
4
3
=2-log23

故答案为:2-log23

阅读理解

“Who needs a shopping mall if you have Taobao?” says Wang Wei, 28, a writer in Beijing.

Taobao, China’s largest online shopping site, has become an important part of Wang Lin’s life. She spends lots of money on Taobao.

A growing number of Chinese Internet users like Wang have found the joys of online shopping. Most online shoppers are students or young workers. More women shop on line than men. Clothing and home-use products are the most popular on line.

It was reported that more than 250 billion yuan was spent on online shopping last year, eighty percent through Taobao.

Taobao means “looking for treasure” in Chinese. People can find almost everything they need on Taobao, from clothes to books , from candies to DVD players.

You may question the security of online shopping. Wang said, “It’s very safe and convenient. Unless you receive the products from the sellers and are satisfied with them, the shop owner will not get the money. You can also get your money back if you want to return the product.

小题1:The underlined word “treasure” in the passage probably means “_______” in Chinese.

A.购物网

B.珠宝

C.生活用品

D.东西小题2:The underlined word “security” in the passage probably means “_______”.

A.quality

B.safety

C.joys

D.convenience小题3:More than _____ billion yuan was spent shopping on Taobao last year.

A.80

B.100

C.200

D.250小题4:Most people shopping on line are ________.

A.young

B.students

C.babies

D.men小题5:The best title for this passage is _______.

A.Wang Wei’s Life

B.Online Shopping in China

C.Where to Shop

D.The Safest Shopping

单项选择题