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某化工材料经销公司购进了一种化工原料共7000kg，购进价格为每千克30元，物价部门规定其销售单价不得高于每千克70元，也不得低于30元，市场调查发现：单价定为70元时，日均销售60kg；单价每降低1元，日均多售出2kg，在销售过程中，每天还要除去其他费用400元（天数不足一天时，按整天计算）．设销售单价为x元，日均获利为y元． （日均获利=销售所得利润﹣各种开支）

（1）求y关于x的函数关系式并写出x的取值范围．

（2）求每千克单价定为多少元时日均获利最多，是多少？

（3）若用日均获利最多的方式销售或按销售单价最高销售，试比较哪一种销售获总利更多，多多少？

答案

解：（1）由题意y=（x﹣30）[60+2×（70﹣x）]﹣400=﹣2x2+260x﹣6400（30≤x≤70）；（2）y=﹣2（x﹣65）2+2050．当单价定为65元时，日均获利最多，是2050元．

（3）当日均获利最多时：单价为65元，日均销售为：60+2×（70﹣65）=70kg，

那么获利为：2050×（7000÷70）=205000元．

当销售单价最高时单价为70元，日均销售60kg，

将这种化工原料全部售完需7000×60×117天，

那么获利为（70﹣30）×7000﹣117×400=233200元．

因为233200＞205000，且233200﹣205000=28200元，

所以，销售单价最高时获利更多，且多获利28200元．

单项选择题 A1/A2型题

患者，女，38岁，确诊乙型肝炎后肝硬化，近1月来右上腹部持续隐痛，腹水迅速增多。腹水检查；外观呈血性，比重1.035，蛋白54g／L。此患者最可能并发（）

A.结核性腹膜炎

B.肝破裂

C.肝癌

D.自发性腹膜炎

E.门静脉血栓形成
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问答题

Libraries form a vital part of the world’s systems of communication and education.
They make available knowledge accumulated through the ages. People in all walks of life use library resources in their work. People also turn to libraries to satisfy a desire for knowledge or to obtain material for leisure-time activity. In addition, many people enjoy book discussions, concerts, film programs, lectures, story hours, and a variety of other activities provided by libraries. Libraries also play an important role in preserving a society’s cultural heritage(遗产). The library ranks as one of society’s most useful service institutions.
The contents of libraries have changed so much through the years that the word library itself is, in a sense, inaccurate. The word comes from the Latin word liber, which means book. Today’s libraries house many books, of course. However, they also have a wide variety of other materials that communicate, educate, and entertain. These materials include magazines, manuscripts (手稿), newspapers, and computer documents.
Audio and visual materials include CDs, audiocassette tapes, videotapes, films, maps, paintings, and photographs.
In addition to regular books, a library may have large-type books, books for the blind, and tape recordings of books, called talking books. Librarians keep pace with the changing contents of libraries to serve as many people as possible. Their efforts have turned libraries into multimedia resource centers.
The expansion of library contents greatly increases the library’s ability to communicate and educate. For example, people interested in classical music can listen to CDs and read books on the topic. Students of agriculture can read magazines and watch videotapes on farming methods. Many people use magazines and newspapers to find the most up-to-date material on current events.
In addition to expanding contents, librarians have developed many kinds of libraries to serve the needs of different people. The materials of each kind of library are selected to meet the needs of a specific group of patrons. School libraries have collections that provide the information needed by elementary and high school students. Public libraries tailor their collections to the general public. Government library collections are geared chiefly toward serving the needs of government officials. Thousands of special libraries provide information for professional people, such as advertising specialists, bankers, editors, engineers, lawyers, physicians, and scientists.
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