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1、二元一次方程组的解法(3),代入消元法解二元一次方程组的步骤?,知识回顾,代入消元法解二元一次方程组的步骤：,想一想,3x +2y =13 3x -2y =5,解：+ 得：6 x=18 x=3,把 x=3代入得： 9+2y=13 y=2,1：利用加减消元法解方程组时在所有的方程组的两个方程中，某个未知数的系数互为相反数，则可以直接 消去这个未知数，如果某个未知数系数相等，则可以直接 消去这个未知数。,填空：,把这两个方程中的两边分别相加。,把这两个方程中的两边分别相减,分别相加,y,分别相减,x,5,练一练：选择,B,2.方程组,3x+2y=13,3x-2y=5,消去y后所得的方程是（ ）,B
2、,A.6x=8,B.6x=18,C.6x=5,D.x=18,3.方程组,用加减法解方程组,3x-5y=6,2x-5y=7,具体解法如下,（1） - 得x=1 (2)把x=1代入得y=-1.,A（1）,B（2）,C（3）,A,想一想,能否对其中的一个方程进行变形，把这个方程组化为相同未知数的系数相等或互为相反数的形式而求解,例5,5x+6y= 7 ,2x+3y=4,自己动手解出方程组例5,用加减法解方程组,方程组的应用,(2)已知3a3xb2x-y和-7a8-yb7是同类项,求xy,即xy=-3,已知（3m+2n-16)2与|3m-n-1|互为相反数 求：m+n的值,即：m+n=7,谈一谈,加减
3、消元法解二元一次方程的步骤?,加减消元法解二元一次方程的步骤?,赠送：七年级英语 期末复习课,Unit 1A Trip to the Silk Road . 单词拼写 ()根据句意及首字母提示补全单词 1. He is friendly to everyone. I b_ he is a good boy. 2. Look! Wang Hong and Zhang Lin are walking a_ the river.,elieve,long,3. He is lonely. Because he has f_ friends here. 4. English is one of the
4、m_ subjects in our school. 5. When you c_ the road, please look left and right.,ew,ain,ross,()根据句意及汉语提示完成句子 1. The river is about four metres _(宽的). 2. John likes all kinds of _(乐器). 3. I am going to Beijing next week. Its a good _ (机会)to try some Beijing Roast Duck.,wide,instruments,chance,4. My mo
5、ther bought some new _(盘子) yesterday. 5. If you run too fast, you will _(跌倒) down. 6. My mother often keeps _(日记) in her free time. 7. Children need to know how to be _(安全).,dishes,fall,diary,safe,8. Class 8 is _(举行) a class meeting now. 9. This summer holiday I went to the Hong Kong- Zhuhai-Macao _
6、(桥梁) with my parents. 世纪 金榜导学号 10. The good news is very _(使人激动).,holding,Bridge,exciting,. 用方框中所给短语的适当形式填空 go for a walk, take a picture, take a tour, be famous as, a few 1. Zhang Jie _a singer. 2. There are _books in the bag.,is famous as,a few,3. Can you _of me before the tall building? 4. Mr Hu
7、likes to _after supper. 5. Lets _during the coming holiday.,take a picture,go for a walk,take a tour,. 根据汉语意思完成句子 1. 我可以用一下你的词典吗? 当然可以。 _ I _ your dictionary? Sure.,May,use,2. 我校正计划和李明的学校一起环游中国。 My school is planning _ _ _ China _ Li Mings school. 3. 这是我校的通知。 _ _ _ _ _ my school.,a,trip,around,with,
8、This,is,a,note,from,4. 我要给李明发一封电子邮件, 告诉他这个好消息。 I _ _ Li Ming _ _ and _ _ the good news. 导学号 5. 丝绸之路是由丝绸制成的吗? _ the Silk Road _ _ silk?,will,send,an,e-mail,tell,him,Is,made,of,6. 我们一起沿着丝绸之路旅行。 We _ _ the Silk Road together. 7. 从山海关到北京有多远? 大约308千米。 _ _ is _ from Shanhaiguan to Beijing ? Its _ 308 _.,t
9、ravel,along,How,far,it,about,kilometres,8. 我们没有足够的时间看到它的全部。 We dont have _ _ _ _ it all. 9. 在一个新地方你会玩得很开心。 You will _ _ _ _ _ in a new place.,enough,time,to,see,have,a,lot,of,fun,10. 这儿有一个标牌, 上面写着“禁止拍照! ” Here is a sign. It says “_ _! ” 11. 成千上万只鸟住在这片森林中。 _ _ birds live in the forest. 12. 在回家的路上, 吉姆
10、买了一个汉堡包。 _ _ _ _, Jim bought a hamburger.,No,photos,Thousands,of,On,the,way,home,Unit 2 Its Show Time! . 单词拼写 ()根据句意及首字母提示补全单词 1. The noodles t_ nice. Would you like some? 2. This computer is w_ 4, 000 yuan.,aste,orth,3. The Chinese i_ paper. 4. Im sorry I didnt r_ you are such a good teacher. 5. In
11、 a_ China, kings lived in the palaces. 6. The hamburgers are w_ food.,nvented,ealize,ncient,estern,()根据句意及汉语提示完成句子 1. He _(仍然) lives in a small house. 2. His _(旅程) to Tibet lasted for a week. 3. Could you _(描述) something about your school life?,still,journey,describe,4. We can get lots of _(经验) from
12、 our life. 5. This is my _(自己的) bedroom. 6. Her smile made me feel warm and lively. It was like a hidden _(财富).,experience,own,treasure,7. I have two sweaters. One is yellow and the _(其 他的) is red. 8. Mr Zhang gave us some good _(建议) on how to learn English well. 导学号 9. We _(应该) walk on the sidewalk
13、. 10. Its raining hard. But he is _(还) standing on the playground.,other,suggestions,should,still,. 用方框中所给短语的适当形式填空 make a joke, work on, take part in, climb up , open ones eyes, talk about, place of interest, be famous as, think about , have a rest 1. Mr Wang is _buying a new car.,thinking about,2.
14、 I will _an English competition next week. 3. How many _are there in your city? 导学号 4. Jim is good at _. 5. Lets _something interesting. 6. Hangzhou _a tourist city.,take part in,places of interest,making a joke,talk about,is famous as,7. Can you _the tree and pick an apple for me. 8. Youre tired. Y
15、ou must _ 9. The writer is _his new novel. 10. This book can _and you should try reading it.,climb up,have a rest.,working on,open your eyes,. 根据汉语意思完成句子 1. 我们在丝绸之路上听说了很多关于他的事情。 We heard _ _ _ him on the Silk Road. 世纪 金榜导学号 2. 在4岁时, 他可以弹钢琴了。 _ _ _ _4, he can play the piano.,a,lot,about,At,the,age,of,3. 这节课持续大约45分钟。 The clas
