题干

命题“xZx2xm<0”的否定是(    )

A:x∈Z使x2+x+m≥0

B:不存在xZ使x2+x+m≥0

C:xZ,x2+x+m≤0

D:xZ,x2+x+m≥0

上一题 下一题 0.0难度 选择题 更新时间:2017-11-04 10:10:00

答案(点此获取答案解析)

D

同类题3

阅读理解

    If you want to become a better reader, what should you know about speed of reading?

    Some people read very rapidly(快速地),while others read very slowly. But which one is better?

    The rapid reader may be a good reader when he reads a storybook for fun. But he may not be able to slow down enough to read directions carefully. He may read so rapidly that he does not take time to understand fully the ideas and information which are important to remember.

    The slow reader may be a good reader when he reads directions for making something. But he may spend too much time in reading a simple story which is meant to be enjoyed but is not important enough to be remembered.

    So, you see, either a rapid reader or a slow reader is not really a good one. If you wish to become a better reader, here are four important things to remember about speed of reading.

    1  Knowing why you are reading will often help you to know whether to read rapidly or slowly.

    2  Some things should be read slowly throughout. Examples are directions for making or doing something, science and history books, and Maths problems. You must read such things slowly or remember each important step and understand each important idea.

    3  Some things should be read rapidly throughout. Examples are simple stories for enjoyment, letters from friends and bits of news from hometown papers.

    4  In some of your reading, you must change your speed from fast to slow and slow to fast, as you go along. You will need to read certain pages rapidly and then slow down and do more careful reading when you come to important ideas.

同类题4

阅读材料,回答下列问题:

材料一

所有的平民都负了富人的债,他们或者是替富人耕种土地,把收成的六分之五作为地租缴纳给债主,自己只能留六分之一,因而被称为“六一汉”或“塞特”;或者以自己人身作债务抵押,可以被债主押收,因而有的在本土成为奴隶,有的被卖到了外国。

材料二

我给了一般人民以恰好足够的权力,也不使他们失掉尊严,也不给他们太多;而那些有钱有势的豪富的人们,我也设法不使他们受到损害;我手执一只大盾,不让任何一方不公平的占着优势。

――梭伦

材料三

梭伦制定的四大财产等级及其权益分配

500斗级

拥有年产500斗(一斗相当于38千克)农产品的地产(这个产量足够提供15个家庭一年所需的基本口粮)的公民,享有选举、充任包括执政官在内的各级国家职官的资格

骑士级

有能力提供马匹和武器装备,并担任骑兵的公民。跻身该等级年收入必须达300~~500斗。享有除司库以外的各级职官的选举和任职资格

双牛级

拥有两头耕牛,其财力可达到自备盔甲、担任重武器装备步兵的公民,大约需要年收入200~~300斗农产品。享有除担任执政官以外的各级职官的选举和任职资格

雇工级

泛指受雇于他人的公民。他们年收入不到200斗,不能担任任何公职,但可参加公民大会和作为陪审员参与司法活动。

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