题干

若x,y满足约束条件 {x+y502xy10x2y+10 ,则z=3x+y的最大值为(   )

A:8

B:9

C:4

D:11

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答案(点此获取答案解析)

D

同类题1

阅读理解

    When someone reads the right book at the right time in his life, it can have a profound effect. Such is the case for the people on this list, who come from all walks of life. These people have singled out a book that they read which had a life-changing effect on them. They, in turn, affected the worlds of science, technology and politics.

1). That Printer Of Udell's—Ronald Reagan

    One book that had a big effect on former President Ronald Reagan as a child was the Christian-book That Printer of Udell's, by Harold Bell Wright. The main character of the book, Dick Falkner, was born into a broken home with an alcoholic father. After losing both of his parents, Falkner moves to a bigger city, called Boyd City to make a living. However, everyone turns Dick down for a job, except for a printer. At the end of the book, Dick heads to Washington, D. C, to become a politician. It's said that the book showed him that good could defeat evil and that the good guys followed a code of morality, which can be seen as a driving factor in his presidency.

2). A Treatise Of Human Nature—Albert Einstein

    Albert Einstein was one of the greatest minds of all time. His name is synonymous with brilliance. So, what book had the biggest effect on such an important mind? It was A Treatise of Human Nature, by David Hume, which was published in 1738. Hume was a Scottish philosopher known for his contributions to philosophical skepticism(怀疑论). Einstein mentioned a few times that A Treatise of Human Nature had a large influence on him. He read the book just before coming up with his famous special relativity theory. In a letter, Einstein said that Treatise helped him formulate the ideas. It was like he already had the ideas in his brain, and Hume helped him to express them clearly.

3). The Aeneid—Mark Zuckerberg

    When Mark Zuckerberg first added his likes to his Facebook profile, he put the book Ender's Game, by Orson Scott Card, as a favorite book. Later, in an interview with The New Yorker, Zuckerberg clarified that the sci-fi classic was one he enjoyed, but it wasn't his favorite. He said that his favorite book is The Aeneid, by Virgil, a Latin epic poem that was written somewhere between 29 - 19 BC about a group of Trojan survivors. Zuckerberg said he first read the book when he was in high school while he was studying Latin and that one thing that stuck with him was Aeneas's drive to follow his fate to build a city that “knows no boundaries in time and greatness".

根据短文内容,选择最佳答案,并将选定答案的字母标号填在题前括号内。

同类题4

阅读下面三篇短文,完成各题。

(甲)归  牧

缪崇群

    一个八九岁大的女孩子,拉着一个小火车头——这是我给水牛起的名字,因为它的身体比一般黄牛要庞大,在田间并不显示得,等它走上了小路,对面遇见,就觉得它格外大,格外重,格外笨,真的像一个小火车头了。

    水牛的鼻子里还发出气咻咻的声响,同火车头停下来的那个情景,可算毫无二致。

    那么小的小姑娘,那么美好的,脸圆圆的小姑娘,她的个子,她的模样,她的服装,和这个水牛比照起来,一个在前头,一个在后面,谁说不像拉着一个小火车头呢?

    那头水牛,走走歇歇,好像意犹未尽;孩子背转过来退着步子走,仿佛听它的便,很有耐性似的。虽然我晓得这个孩子念家的心切,牛却不慌不忙地,并不随随便便就让这个小主人牵了回去。

    我看见这个小女孩的腕上,有一只还套着一个人造象牙的小手镯。

    她们先走在我的前面,不久就落在我的后边了。

    我再回头,她们已经落在苍茫的暮色里。

    她们不比那热带地方的朝廷,坐在象背的锦鞍上,华丽伞盖底下的王孙公主们更高贵些,更令人羡慕吗?

【注】①选自《石屏随笔》,云南人民出版社2008年版,缪崇群(1907-1948),我国现代作家。

(乙)患肺痨病的小女孩

希梅内斯

    白石灰墙的冷清病房中央,她直挺挺地坐在孤独的椅子上,面色苍白无神,像株枯萎的香甘松。医生要她下乡晒点三月的阳光,不过可怜的孩子身体太弱了。

     “就快走到桥边的时候,”她告诉我,“你知道吗,老伯伯,我就透不过气来。”

    她微弱、断绩的童音疲倦地弱去,就像夏天的微风时而欲吹又止。

    我让她骑著普儿出来透透气。一路上,削瘦垂死的脸庞笑得多开心,满是黑眼珠、白牙齿。

    妇人都跑到门口看我们走过。普儿放慢脚步,彷佛知道背上驮的是栗脆弱的玻璃百合。兴奋和喜悦改变了小女孩的容貌,配上一身纯白的衣裳,看起来就像路过小镇赶往南方的天使。

【注】①选自《小毛驴与我》,团结出版社2005年版,林为正译。希梅内斯(1881-1958),西班牙著名诗人。②普儿:小毛驴的昵称。

(丙)玩  具

泰戈尔

    孩子,你真是快活呀!一早晨坐在泥土里,耍着拆下来的小树枝儿。

    我微笑着看你在那里耍弄那根折下来的小树枝儿。

    我正忙着算账,一小时一小时在那里加叠数字。

    也许你在看我,心想:“这种好没趣的游戏,竟把你一早餐的好时间浪费掉了!”

    孩子,我忘了聚精会神玩耍树枝与泥饼的方法了。

    我寻求贵重的玩具,收集金块与银块。

    你呢,无论找到什么便去做你的快乐的游戏。我呢,却把我的时间与力气都浪费在那些我永不能得到的东西上。

    我在我的脆薄的独木船里挣扎着,要航过欲望之海,竟忘了我也是在那里做游戏了。

【注】①选自《飞鸟集·新月集》,湖南文艺出版社2011年版,郑振铎译,泰戈尔(1861-1941),印度文学家。