问题 问答题

在抛物线y=1-x2与x轴所围成的平面区域内,做一内接矩形ABCD,其一条边AB在x轴上(如图所示).设AB长为2x,矩形面积为S(x).

(1)写出S(x)的表达式.

(2)求S(x)的最大值.

答案

参考答案:

(1)S(x)=2xy=2x(1-x2)=2x-2x3.

(2)s’(x)=2-6x2.

由于驻点唯一,且实际问题有最大值,所以为最大值.

阅读理解

阅读理解。

     I am wearing a small red ribbon this morning to remind myself and others around me that today is World

AIDS Day.

     The red ribbon, an international symbol of AIDS awareness, is gaining increasing public recognition as

more Chinese, from top leaders to movie stars, wear it today.

     Gone were the days when the topic of HIV/AIDS was a public and media taboo (禁忌). Over the past few

years, we have watched, read and heard many stories from doctors, volunteers and public health officials at

the forefront of HIV/AIDS prevention and treatment.

     Quite a few people with HIV/AIDS have come forward to share their experiences on TV or in the media.

     The local and central governments have become more forthcoming (be helpful) with their new prevention

and treatment programmes, and financial input. The latter rose from less than 1 million yuan (US$ 121,000) in

1986 to a pledge of 800 million yuan (US$98.8 million) in the year of 2006.

    The change from silence to public and media campaigns with official promises has been remarkable,

especially since China battled through the SARS crisis.

     But have we got a full understanding on HIV/AIDS? What do we know about the extent of HIV/AIDS in

China?

     The figures, ranging from confirmed cases to estimates, remain debated. After all, no more than a year has

passed since the policy of free medical tests was make public. Unknown numbers from the high-risk groups

drug addicts and people working in sex- related place as well as farmers who once sold blood could still be

reluctant to come forward.

1. what does the red ribbon stand for?

A. AIDS

B. World AIDS Day

C. AIDS awareness

D. AIDS prevention and treatment

2. Which of the following is Not true according to the text?

A. The topic of HIV/AIDS was a public and media taboo in the past.

B. The topic of HIV/AIDS is now still a public and media taboo.

C. Now a lot of people with HIV/AIDS have come forward to share their experiences on TV.

D. The writer wears a small red ribbon because today is World AIDS Day.

3. In paragragh 5 "The latter" refers _______.

A. financial input

B. new prevention programmes

C. new treatment programmes

D. the central governments

4. We can learn from the text that high- risk groups of HIV/AIDS in

China include the following EXCEPT ____.

A. drug addicts

B. people working in sex-related place

C. farmer who once sold blood

D. people getting close to those affected with HIV/AIDS

5. What is the best title of the passage?

A. The Red Ribbon

B. Always keep red ribbon in sight

C. About AIDS

D. Help people with AIDS

多项选择题