您所在的当前位置：高中数学试题 >

四种命题

> 命题“ x∈R，x 3﹣2x+1=0”的否定是 [ ] A． x∈R，x 3﹣2x+1≠0 B．不存在x∈R，x 3﹣2x+1≠0 C． x∈R，x 3﹣2x+1=0 D． x∈R，x 3﹣2x+1≠0

问题：

发布时间：2024-09-08

命题“ x∈R，x ³﹣2x+1=0”的否定是
[ ]
A． x∈R，x ³﹣2x+1≠0
B．不存在x∈R，x ³﹣2x+1≠0
C． x∈R，x ³﹣2x+1=0
D． x∈R，x ³﹣2x+1≠0

参考答案：

提问用户：OP***3Da

可能感兴趣的题目：

1 （8分）铁是人类较早使用的金属之一，根据所学铁及其化合物的知识，回答下列问题：（1）下列各物质中，不能和单质铝反应的物质是（填下列各项序号）。 ①Fe ②FeCl 3 ③FeSO 4 （2）向沸水中逐滴滴加1mol·L -1FeCl 3溶液，至液体呈透明的红褐色，实验得到的分散系属于（填“溶液”“浊液”或“胶体”），所得到的分散系中的分散质具有的性质有如下的（填写序号）。 ①电泳 ②透过半透膜 ③聚沉 ④具有强还原性（3）电子工业需要用30%的FeCl 3溶液腐蚀敷在绝缘板上的铜，制造印刷电路板。请写出FeCl 3溶液与铜反应的化学方程式：；证明反应后的溶液中存在Fe 3+的实验方法是。
2 ATP在生物体的生命活动中发挥着重要的作用，下列有关ATP的叙述，不正确的有几项 ①人体成熟的红细胞、蛙的红细胞、鸡的红细胞中均能合成ATP ②若细胞内Na +浓度偏高，为维持Na +浓度的稳定，细胞消耗ATP的量增加 ③ATP中的“A”与构成DNA、RNA中的碱基“A”不是同一物质 ④ATP是生物体生命活动的直接供能物质，但在细胞内含量很少 ⑤能进行有氧呼吸的细胞不一定含有线粒体但一定含有相关的酶，可产生ATP ⑥ATP中的能量可以来源于光能、化学能，也可以转化为光能和化学能 ⑦人在寒冷时，肾上腺素和甲状腺激素分泌增多，细胞产生ATP的量增加 ⑧细胞中一切耗能的生命活动都是由ATP提供的，因为ATP是细胞的能量“通货” [ ] A．0项 B．1项 C．2项 D．3项
3 Mobile phones are an important business tool for farmers in rural areas. But they also put a valuable educational tool in their hands. The University of Illinois in the United States has a project called SAWBO—Scientific Animations Without Borders. It produces educational videos that can be downloaded to cell phones. The goal is to help people in developing countries improve their lives. One video shows farmers how to make a natural insecticide from neem seeds to prevent insect damage to crops. The process starts with sorting and drying the neem fruits. Then let the fruit dry in the sun for about three or four days, until they become brown. Using a mortar(碾槌) and stick, the fruits are slightly pounded to remove the shells from the fruits without breaking the seed inside. The videos use computer animation(动画). Some of the animated characters are a little funny looking-like a farmer with a long nose. But the subjects are serious, including a health video on preventing cholera(霍乱). Team member Francisco Seufferheld says the information in the videos is meant to be quickly understood. He says, “The information is digested in such a way that in two minutes, we can transmit a complex idea.” The researchers tested the seven-minute video on seven mobile phones. They wanted to see if people would share the video using Bluetooth wireless technology. With Bluetooth, files can be passed to a nearby phone even if neither phone is connected to the Internet. As a result, in one month, the video had spread to one hundred eighteen people in fifty different villages. “This is just incredible impact,” said Francisco Seufferheld. The team has made a few videos so far. These are available in a total of eighty languages, dialects and accents. Professor Barry Pittendrigh says there are plans for more videos later this year. 小题1:What is the text mainly about? A．A best-selling mobile phone B．A valuable educational project for farmers C．United States support for developing countries D．A new type of scientist –farmer relationship 小题2:The SAWBO program is introduced in order to ____. A．raise farmers’ standard of living B．do some research on mobile phones C．develop farmers’ practical skills D．help farmers prevent insect damage to corps 小题3:The biggest advantage of the program is that it______. A．includes health video on preventing cholera B．can be passed to farmers using Bluetooth technology C．can be used to sort and dry the neem fruits D．is easy for farmers to understand 小题4:Which of the following words can best take the place of the word “ pound” in the 3 rd paragraph? A．moved B．beat C．picked D．cut
4 有一幅广告幽默画，画的是几个行人在看一家饭店外贴的告示，上写：“快进来吃饭吧，否则你我都得挨饿。”这幅广告画的经济学寓意是 A．生产是消费的动力 B．商品生产和交换活动背后隐藏着人与人的关系 C．生产与消费相互决定 D．生产者以满足消费者的需要为其经营目的
5 1－丁醇和乙酸在浓硫酸作用下，通过酯化反应制得乙酸丁酯，反应温度为115℃～125℃，反应装置如右图。下列对该实验的描述错误的是(　　) A．不能用水浴加热 B．长玻璃管起冷凝回流作用 C．提纯乙酸丁酯需要经过水、氢氧化钠溶液洗涤 D．加入过量乙酸可以提高1－丁醇的转化率
6 _____ their inexperience, they’ve done a good job. A．Given B．Supposed C．Considered D．Concluded
7 美国学者詹姆斯?麦格雷戈?伯恩斯在所著《罗斯福》中，把罗斯福对付国会的方法列举出来如下：“充分利用宪法规定的权力，诸如否决权。选择有利时机。在行政部门草拟议案。几乎需要不断地施加压力，但却要机智巧妙。用人必须审慎。亲自说服立法领导人。诉诸国民公断。”这说明罗斯福新政时 [ ] A．并未动摇美国宪政的基础 B．选举议院议长时进行干涉 C．对三权分立制度进行了改革 D．国家权力重心在参众两院
8 把地球上的一个秒摆(周期等于2s的摆称为秒摆)拿到月球上去，它的振动周期变为多少？已知：地球质量M 地=5.98×10 24kg，半径R 地=6.4×10 6m，月球质量M 月=7.34×10 22kg，半径R 月=1.74×10 6m。　　
9 一 I"d like to take a week"s holiday. 一 _____.We"re too busy. [ ] A. Don"t worry B. Don"t mention it C. Pardon me D. Forget it
10 I’m sorry, but I didn’t mean to keep you waiting here for a long time. Can you ______ me? A．forgive B．satisfy C．apologize D．remind