您所在的当前位置：初中数学试题 >

整式的混合运算

> 王老师让同学们计算：“当 a= 1 2 ， b=- 1 3 时，求（a+b）（a-b）+（a+b） 2-2a（a+b）的值”．小明同学在解题时将题目中所给的条件“ a= 1 2 ， b=- 1 3 ”看成了“ a= 1 2 ， b= 1 3 ”，而算出的结果却是正确的，你知道为什么吗？

问题：

发布时间：2024-09-09

王老师让同学们计算：“当 a=

1

2

， b=-

1

3

时，求（a+b）（a-b）+（a+b） ²-2a（a+b）的值”．小明同学在解题时将题目中所给的条件“ a=

1

2

， b=-

1

3

”看成了“ a=

1

2

， b=

1

3

”，而算出的结果却是正确的，你知道为什么吗？

参考答案：

提问用户：mw***kDq

可能感兴趣的题目：

1 已知代数式0.5a的值为2，那么4a 2﹣a+1值为 [ ] A．61 B．59 C．13 D．1
2 求 x+11-6 x+2 + x+27-10 x+2 =1的实数根的个数．
3 If you have a problem with speaking, you can do several things. Listen to English as much as possible. You can learn a poem(诗) or a song by heart. You can also learn more dialogues（对话）. And practice speaking with your friends as much as you can. Many people find it difficult to listen to English. The answer is to listen as much as you can. However, don’t do too much at one time. It is better to practice listening for five minutes every day. Don’t sit down and listen for an hour at a time. That’s too much! Do choose listening passages that are interesting and not too difficult. Choose（选择） tapes（磁带） on which the people speak clearly and not too fast. Take it easy， at first. Success with simple tapes at the beginning is the answer. Later on you can practice with tapes that are more difficult. Finally, how can you learn to write well? How do you use little words like in, on, of and for? There are two answers to this. First, do some study with new words. Keep a list of verbs like look for, look after and so on. Second, read as much English as possible. There are many things that can’t be learnt. You must see them in books many times. Then you’ll be able to use them correctly(正确地) yourself. So, in order to write well, you must first learn to read much.This passage is about English ______ .If you ______ , you can speak well.Which of the following is right according to the passage?Which of the following ways can help you to improve（提高） your written English? Which of the following is not right according to the passage? spelling, listening, grammar and reading,listening, speaking, reading and writing,taking exams, pronunciation, reading and writing,pronunciation, reading, listening and writing,spelling, listening, grammar and reading,listening, speaking, reading and writing,taking exams, pronunciation, reading and writing,pronunciation, reading, listening and writing,learn more dialogues,learn a poem or a song by heart,practice speaking with your friends as much as you can,all above,learn more dialogues,learn a poem or a song by heart,practice speaking with your friends as much as you can,all above,It’s better to listen to English for a long time every day.,At the beginning, you’d better choose the tapes on which the people speak quickly.,At first you should begin with simple tapes for listening.,Few people think it hard to listen to English.,It’s better to listen to English for a long time every day.,At the beginning, you’d better choose the tapes on which the people speak quickly.,At first you should begin with simple tapes for listening.,Few people think it hard to listen to English.,Buy books of writing practice. ,Read as much as possible.,Do some study with new words. ,Both B and C.,Buy books of writing practice. ,Read as much as possible.,Do some study with new words. ,Both B and C.,Many people find it difficult to listen to English.,Sit down and listen for an hour at a time.,Learn a poem or a song by heart can improve your speaking.,To improve speaking, you can practice speaking with your friends as much as you can.,Many people find it difficult to listen to English.,Sit down and listen for an hour at a time.,Learn a poem or a song by heart can improve your speaking.,To improve speaking, you can practice speaking with your friends as much as you can.
4 长大成人的重要标志是 A.对自己负责 B.对他人和社会负责 C.具有强烈的责任意识 D.要懂得关爱他人
5 与方程x-1=2x的解相同的方程是 A.x=2x+1 B.x-2=1+2x C.x=2x+3 D.x=2x-3
6 东东上幼儿园和妈妈分开时哭了起来，但妈妈离开不久，他便恢复了平静，开心的跟其他小朋友一起玩耍。妈妈来接他放学时，他高兴地投入妈妈的怀里。东东的这种依恋行为表现属于（）。 A 回避型依恋 B 无依恋型 C 安全型依恋 D 反抗型依恋
7 凡施工图结构、工艺、平面布置等有重大改变，或变更部分超过图面( )的，应当重新绘制竣工图。 A 1/2 B 1/3 C 1/4 D 1/5
8 读世界某区域1月和7月海平面气压(单位：hPa)和风向图，①～⑥处的箭头表示风向，图中形成的气压中心，与其控制地区原气压带特点相似的是(　　) A．甲 B．乙 C．丙 D．丁
9 【题文】阅读下列材料，回答问题。（7分）材料一：《汉字英雄》是“河南卫视”与“爱奇艺”联手打造的中国国内首档大型网台联动的文化综艺类节目。节目集综艺性和知识性于一体，将文化和娱乐相融合，集合全国各地识字最多的青少年倾情参与，为青少年打造了一个展示自己掌握汉字水平和个性的机会和舞台。材料二：一档形式单纯、简朴的“冷节目”—《中国汉字听写大会》，近日出乎意料地黏住了广大电视观众，热了起来。据统计，节目播出后的同时段收视率飙升4倍，微博上更是登顶话题热门榜，点击突破18万，百度搜索高达42万。该节目最初在中央电视台科教频道崭露头角，后因受欢迎而增设在中央电视台综合频道晚上的黄金时段播出。比赛引发的“提笔忘字”、“国人书写能力普遍退化”等有关汉字之忧的讨论，也频繁见诸互联网和各大报端。节目让广大观众在电视荧屏前领略了中华汉字之美，唤醒了国人对汉字的记忆与热情，对汉字具有的传承传统文化的功能用大众传媒的方式予以了再度开掘，值得充分肯定和期许。材料三：北京市教委昨天公布《2014-2016年高考高招改革框架方案》，并向社会征求意见。意见稿指出，从2016年起，高考语文分值由150分增至180分，文、理科综合分值由300分增至320分。英语考试将实行社会化考试，一年两次考试，学生可多次参加，按最好成绩计入高考总分，成绩3年内有效，考试分值也由150分降低到100分。【小题1】给材料二拟一个标题（不超过15个字）。（2分）【小题2】综合上述材料，你能得出什么结论？（2分）【小题3】对电视荧屏上出现的“汉语热”现象，有人认为，有一种文化倾向在抬头，即企图要求今天的学生，把美好的青春用于死背硬记那些僵尸般的文字。“我没有听见谁为学生们提供一种新的学习方式，而满耳朵灌输的是一套就是在八股时代也少之又少的酸腐腔调。”针对上述观点，你是支持还是反对呢？说说你的理由。(3分)
10 如图为家蚕发育的全过程，请写出他的正确顺序 A.①③②④ B.④③②① C.①②④③ D.④①②③