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人教版新目標初中英語八年級下冊What were you doing when the UFO arrived教案2篇
(一).知識方面: 1.培養(yǎng)學(xué)生能運用過去進行時來描述、談?wù)撨^去某個時間正在發(fā)生的事情或動作的意識和能力，能就過去某個時間正在發(fā)生的動作做出正確的描述。 2.培養(yǎng)學(xué)生的想象力和角色扮演的合作能力。 3.培養(yǎng)學(xué)生講述過去發(fā)生的事情經(jīng)過的能力。能正確運用一般過去時來講述故事。 (二).技能方面: 1.本單元的語言目標是Talk about past events and tell a story（談?wù)撨^去的時間和講述一個故事），圍繞這一目標，要涉及句型： What were you doing when the UFO arrived? ----I was sitting in the barber’s chair. The barber was cutting my hair. 因此必須學(xué)習(xí)standing、studying、cleaning、sleeping、cooking、making、eating、cutting、等表示地點的詞，以便為上述句型提供語言材料。2.學(xué)習(xí)過去進行時的有關(guān)知識。Was/were+現(xiàn)在分詞，是該時態(tài)的表達式。 3.在學(xué)習(xí)過程中，要區(qū)分The boy was walking down the street when the UFO landed.和While the boy was walking down the street, the UFO landed.這兩種由when和while引導(dǎo)的狀語從句的句型結(jié)構(gòu)。注意它們的不同。
人教版新目標初中英語八年級下冊Why don’t you get her a scarf教案
教師帶領(lǐng)學(xué)生復(fù)習(xí)有關(guān)描述寵物的詞匯，采用教師提問學(xué)生回答的方進行。如：T：What animals do you think would be good pets？What animals do you think would be bad pets？What do you think are good animals for a six-year-old child？然后學(xué)生進行 pairwork 練習(xí)。Task two: 師生互動，學(xué)習(xí)探究 1、播放3a部分的錄音，引導(dǎo)學(xué)生一邊聽錄音，一邊跟讀。2、通過聽錄音學(xué)生回答以下問題：Why do you think pot-bellied pigs are popular？What are the advantages and disadvantages of keeping such a pet？教師對學(xué)生的回答進行及時點評。3．學(xué)習(xí)范文，學(xué)習(xí)重點短語，為下步的模仿寫作提供語言素材。T :1. )Have you ever kept a pig as a pet?Do you like pigs? St.:No.…Why don’t you like to keep a pig? St: No.They’re too dirty and lazy(Do you know in some foreign countries like Hollyland, Australia,pigs are the most popular pet.there’s a kind of pig.(圖)it has an interesting name? it ‘s called a pot-bellied pig.) Now,let’s learn an article about this kind of interesting pet.2.)play the tapeSt.:Listen and repeat3.)show some Qs on computer(本子St.: read silently,then answerthe Qs(本子)4.)Ask ss. Close book and retell this passage.(what is a pot-bellied pig? Is it a good or bad pet? ) St.: retell it to each other“A pot –bellied pig is a popular pet now…”5.read the article together.St.:.practice reading
人教版新目標初中英語八年級下冊Would you mind turning down the music教案
Step 4. Group work (4)1. Ask a pair of students to read the dialogue. Say, This activity provides speaking, listening and writing practice using the target language.2. Ask students to complete the work in groups.3. Check the answers with the whole class. 4. Explain some of the language points. Step 5. Word review (Self check 1)1. Ask students to read the words and the phrases given. 2. Fill in the blanks with proper forms of these words to complete the sentences. 3. Check the answers with the whole class. Homework:Do activity 2 on page 57 after class. Period 6Teaching aims: 1. Teach vocabulary words and the useful expressions. 2. Enable the students to learn etiquette in different culture. 3. Help the students learn how to behave politely in public places and in daily life. Teaching procedures:Step 1. RevisionHelp students to review the function of making requests through a free talk. Then lead them to the topic of etiquette. Explain the meaning of etiquette. Or, ask students to look it up in the dictionary. Step 2. Pre-reading (Section 1)1. Ask students to read the picture and make a list with their partner about how many rules of etiquette can be seen being broken.
人教版新目標初中英語九年級上冊Teenagers should be allowed to choose their own clothes教案2篇
Step 1 Greeting Greet the class and check the homeworkStep 2 A duty report The S on duty gives a report on the rules in his home and lead in 3a “Sun Fei’s and Wu Yu’s rules” Step 3 ReadingSs read the conversation and write the two girls’ rules in the chart. Check the answers.Get Ss to read after the tape and then read aloud by themselves. Then, T explains the language points.Step 4 Pairwork 3bRole play. Use the information in chart to practice with the conversation in 3a covered. They can look at the sample conversation in the right box.Step 5 Task 2 “Who’s the best reporter?”Make a survey by asking any 5 students the questions in the chart in activity 4. Then give out a report about it. See who is the best reporter? And the best reporter will get a nice ball-pen.Step 6 Summary and homework:Write out the report in your exercise-books.Period ThreeStep 1 Greeting and a duty reportThe S gives a duty report talking about his experience of being late for school. Lead in the question “Do you ever get to school late? How often do you get to school late? Always, usually, sometimes, or never?Step 2 1a Get Ss to finish writing.Step 3 Pairwork 1b Get Ss to talk about their answers with their partners using the sample conversation in the box on the right.Step 4 Listening practice2a Lead-in: What will happen if you get to school late? What about Peter? Let’s listen to a conversation between Peter and his father. Get Ss to finish 2a (As usual, for the first time, Ss only listen.) Check the answers.
人教版新目標初中英語九年級上冊I like music that I can dance to教案
教學(xué)目標: 1. Express preferences2. Talk about one’s likes and dislikes and the reasons3. Learn to express one’s opinions 4. Learn to write a reply 語言功能： 1) Talk about one’s preferences, using t he relative clause2) Talk about people’s likes and dislikes and the reasons3) Talk about opinions語言結(jié)構(gòu)： Relative clauses with that and who語言目標：What kind of music do you like?I like music that I can sing along with.I love singers who write their own music.We prefer music that has great lyric.重點詞匯及短語：heart, photography, interest, class, whatever, miss, okay, expect, sweet, taste, itself, laboratory, cancer, increase, biscuit, main, care， prefer… to…, remind somebody of …, dance to, sing along with, be sure to, interest somebody, make somebody adj., to be honest, suit somebody, on display, catch up教學(xué)重難點：What do other people think of the different kinds of things? How to express one’s opinions? 學(xué)習(xí)方式：討論，合作學(xué)習(xí)情感目標：通過本單元的學(xué)習(xí)，能提高學(xué)生的藝術(shù)鑒賞能力和審美情趣，并引導(dǎo)學(xué)生養(yǎng)成健康的飲食習(xí)慣。課時安排5課時第一課時：Section A: 1a-2c第二課時：Section A : 3a-4第三課時：Section B:1-2c, Self check2第四課時：Section B: 3a-4, Self check1第五課時：Self check ReadingI like music that I can dance to.
人教版新目標初中英語九年級上冊I used to be afraid of the dark教案
內(nèi)容提示1．本單元主要內(nèi)容是學(xué)會used to結(jié)構(gòu)。Used to +動詞原形表示過去經(jīng)常、以前常常，只用于過去式中，用來表示現(xiàn)在已不存在的習(xí)慣或狀態(tài)。例如：They used to play football together．他們過去常在一起蹋足球。（現(xiàn)在不在一起踢了)2．used to的疑問形式和否定形式為Did you use to…?和I didn’t use to… 也可以用Used you to…?和I used not to…但現(xiàn)在多使用前者。例如：Did you used to swim in the river? 你過去常在河里游泳嗎?I didn’t use to play the piano． 我以前并不經(jīng)常彈鋼琴。教學(xué)目標一、學(xué)習(xí)目標（Language Goal） 1．學(xué)會陳述自己過去常做的事情。2．學(xué)會陳述自己過去的愛好等。3．能夠表達自己現(xiàn)在和過去在外表、性格、娛樂等方面的變化。4．能夠表達朋友、家人等現(xiàn)在和過去的變化。二、語言結(jié)構(gòu)（Language Structures） 1．I used to be short when I was young. 我年輕時個子很矮。 2． —Did you use to have straight hair? 你過去是直發(fā)嗎？—Yes, I did. 是的。 3． —Did you use to play the piano? 你過去彈鋼琴嗎？—No, I didn’t. 不，我不彈。 4．I used to be afraid of dark. 我過去害怕黑暗。 5．I’m terrified of the snakes. 我害怕蛇。
人教版新目標初中英語九年級下冊By the time I got outside, the bus had already left教案
Ⅰ． Teaching Aims and Demands1． Knowledge Objects（1） Key Vocabularyoversleep（2） Target LanguageWhat happened?I overslept． And by the time I got up, my brother had already gotten in the shower．2． Ability Objects（1） Teach the students to use the new words．（2） Train the students to narrate past events with the Past Perfect Tense．（3） Train the students' listening and speaking skills with the target language．3． Moral ObjectIt’s a good habit to go to bed early in the evening and get up early in the morning． So you’ll never be in a hurry in the morning．Ⅱ． Teaching Key Points1． Key Vocabularyoversleep2． Target LanguageNarrate past events with the Past Perfect TenseⅢ． Teaching Difficult Points1． Train the students to narrate past events with the Past Perfect Tense．2． Train the students to understand the target language in spoken conversation．Ⅳ． Teaching Methods1． Thinking of examples from the students' real lives．2． Making sentences by looking at the pictures．Ⅴ． Teaching AidA tape recorderⅥ． Teaching ProceduresStep I Revision1． Revise the language points in Unit 8．Ask some questions like this: What volunteer work would you like to do?Help the students to answer, I’d like to…/I love to…/I hope to2． Practice the dialogue in Activity 3c on page 62 again． Get students to role play the similar dialogues with the following．
人教版新目標初中英語九年級上冊It must belong to Carla教案
一、Section A該部分有4個模塊。第一模塊圍繞Whose volleyball is this? 這一話題展開思維（ 1a）、聽力（1b）、口語（ 1c）訓(xùn)練；第二模塊圍繞上一模塊中的話題進行聽力（ 2a-2b）、口語訓(xùn)練（ 2c）；第三模塊繼續(xù)圍繞前兩個模塊中的“making inferences”展開訓(xùn)練。訓(xùn)練形式為閱讀排序（ 3a）和兩人問答（3b）；第四模塊仍就上一話題展開討論。二、Section B該部分有4個模塊。第一模塊要求根據(jù)圖畫和所提供的單詞寫出合理的句子；第二模塊在聽力（ 2a-2b）和分角色口語訓(xùn)練（ 2c）的基礎(chǔ)上，繼續(xù)進行“推測”訓(xùn)練; 第三模塊圍繞“Strange events in Bell Tower neighborhood”這一話題展開閱讀（ 3a）和寫作（3b -3c）訓(xùn)練；第四模塊以dream為話題展開小組活動。三、Self Check該部分有3個模塊。第一模塊以填空形式對所學(xué)詞匯進行訓(xùn)練；第二模塊就8個諺語展開閱讀和討論。
人教版新目標初中英語九年級下冊Rainy days make me sad教案
1. 教材分析本單元以how do things affect you？為話題, 從顏色、天氣、音樂、廣告、產(chǎn)品等方面談?wù)摿送饨缡挛锶绾斡绊懭说男那椤Ｒ髮W(xué)生掌握表達某物或某事給人帶來的感覺、看法或影響等。共設(shè)計了四個部分的內(nèi)容：Section A 該部分有4個模塊：第一模塊圍繞Which restaurant would you like to go to?這一話題展開思維（1a）、聽力（1b）、口語（1c）訓(xùn)練；第二模塊圍繞How does music affect you? 進行聽力（2a-2b）、口語訓(xùn)練（2c）；第三模塊繼續(xù)圍繞how do colors in the restaurant affect you這一話題展開訓(xùn)練，訓(xùn)練形式為閱讀和問題體驗（3a）和小組活動（3b）；第四模塊仍就How do things affect you這一話題以調(diào)查的形式展開討論。Section B該部分有4個模塊：第一模塊圍繞產(chǎn)品廣告對人們的影響這一話題以“配對”（1a）與“列舉”（1b）兩種形式展開訓(xùn)練；第二模塊繼續(xù)圍繞How do things affect you? 進行聽力（2a-2b）、口語對話訓(xùn)練（2c）；第三模塊圍繞“Advertising”這一話題展開閱讀（3a-3b）和寫作（3c）訓(xùn)練；第四模塊圍繞How posters affect you這一話題以口語訓(xùn)練形式展開小組活動。
人教版新目標初中英語九年級下冊Could you please tell me where the restrooms are教案
Step Ⅰ RevisionCheck homework． Ask a few students to read the article in 3a．Then ask a few students to read their guides．Step Ⅱ Part 1Look at the words in the box． Ask a student to read them． Make sure the students understand the meaning of the words． You are to fill in the blanks with the words． In some cases, students may need to use another form of the word, for example adjusting for tense or subject/ verb agreement．Ask students to fill in the blanks on their own．Check the answers． Step ⅢPart 2Go through the instructions with the class．Look at the example with the students．Ask students what the answer would be．Ask a student to read the question and answer it．Excuse me, could you tell me where the bank is, please?The bank is across the street from the shopping malt．Get students to complete the work in pairs．Check the answers． Ask a few students to read their questions．Step Ⅳ Just for Fun!Ask all the students to read the conversation． Ask: What is funny about this cartoon? Help students to explain． A Martian is a person from the planet Mars．There is no such thing as Martian food on Earth, and the clerk looks silly because he is trying to think of where there is a Martian restaurant．Invite some pairs of students to present this conversation to the rest of the class．Step Ⅴ Summary and HomeworkIn this class, we’ve done much writing practice using the key vocabulary words and the target language presented in this unit． After class, please finish the questions in 2 in your exercise books． Then finish the exercises on pages 47～48 of the workbook as well．The Seventh Period Ⅰ Teaching Aims and Demands1． Knowledge Objects（1） Key Vocabularyimage, adventure, jealousy, hero, crime, journey, brave, no longer, show interest in, take it easy, become interested in, plain looks（2）Text:Grown-ups like cartoons, too．2． Ability Objects（1） Fast-reading to get a general idea of the text．（2） Careful-reading to get the detailed information in the text．
人教版新目標初中英語九年級下冊I’ll help clean up the city parks教案
Talk about offering help (P60)I’ll help clean up the city parks.A: I’d like to work ...B: You could help ...Talk about ways to tell people about the Clean-Up Day (P61)We need to ...We can’t ...I’ll ...Talk about the work the volunteers do (P62)These three students all volunteer their time to help other people.Somebody loves to ... / helps ... / plans to ... / wants to ...A: What do you like doing?B: I like ... A: What kind of volunteer work do you think I could do?B: You could ...1. 重點詞匯advertisement, fix, repair, pleasure, blind, deaf, shut, carry, specially, fetch2. 認讀詞匯hunger, homeless, cheer, clean-up, sign, establish, major, commitment, elementary, veterinarian, coach, similar, call-in, strategy, disabled, organization, unable, support, appreciate, donation, part of speech, pronoun, adverb, preposition, conjunction, donate, Jimmy, Sally3. 詞組clean up, cheer up, give out, put off, set up, think up, take after, fix up, give away, put up, hand out, work out, at once
人教版新目標初中英語九年級下冊We’re trying to save the manatees教案2篇
本單元主要圍繞著有關(guān)瀕臨滅絕的動物這一話題，學(xué)習(xí)了應(yīng)該怎樣保護我們的環(huán)境，以及就某一問題展開辯論。目標提示語言目標能夠運用所學(xué)知識，就某一問題展開辯論。認知目標1、復(fù)習(xí)一些語法：現(xiàn)在進行時、一般現(xiàn)在時、用used to 表示一般過去時、現(xiàn)在完成時、一般過去時的被動語態(tài)。2、學(xué)會表達同意和不同意。3、學(xué)會以下基本句型：We’re trying to save the manatees.Manatees eat about 100 pounds of food a day.There used to be a lot of manatees.In 1972,it was discovered that they were endangered.Some of the swamps have become polluted.情感目標了解一些瀕臨滅絕的動物的生活習(xí)性和瀕臨滅絕的原因，教育學(xué)生應(yīng)該如何保護環(huán)境。教學(xué)提示充分利用多媒體等教學(xué)設(shè)備，創(chuàng)設(shè)與本課話題相關(guān)的情境，如各種不同種類的動物、動物園以及有關(guān)環(huán)境的畫畫等等。圍繞著本單元的教學(xué)目標，設(shè)計一些貼近學(xué)生實際的教學(xué)任務(wù)，如讓學(xué)生談?wù)撟约鹤钕矚g的動物，如何拯救瀕危動物，如何保護環(huán)境等等。讓學(xué)生根據(jù)所學(xué)知識，就動物園是否對動物有利以及其他的話題進行辯論。
人教版新目標初中英語九年級下冊You’re supposed to shake hands教案
教學(xué)目標：1. 掌握本單元一些重點詞匯的寫法和用法。2. 學(xué)會自如談?wù)摬妥蓝Y儀。Step 1 RevisionAsk some students to retell the customs at the table in France in the passage in 3a.Step 2 Self checkPart 1. Fill in each bland with the correct word given. Students do the exercises by themselves at first. Then check the answers. Ask the students to comprehend the sentences and help them point out uses of some words, like “arrive (at / in) sw., spend time / money on sth , spend time / money (in) doing sth.”Part 2. Read about Fan Ling’s experience in a western restaurant. Understand the passage. Point out some key points in the passage.1. be / get used to doing sth. 習(xí)慣做某事2. begin with = start with 以….開頭3. crowd v. 擠滿，塞滿 the crowd 人群 crowded adj. 擁擠的Then students discuss about how she would solve her problem. Ask some to share their stories with others.Part 3. Complete the crossword by looking at the sentences on the left. Then check the answers.
北師大初中八年級數(shù)學(xué)下冊一元一次不等式組的解法教案
把解集在數(shù)軸上表示出來，并將解集中的整數(shù)解寫出來．解析：分別計算出兩個不等式的解集，再根據(jù)大小小大中間找確定不等式組的解集，再找出解集范圍內(nèi)的整數(shù)即可．解：x＋23<1?、?，2（1－x）≤5?、冢散俚脁＜1，由②得x≥－32，∴不等式組的解集為－32≤x＜1.則不等式組的整數(shù)解為－1，0.方法總結(jié)：此題主要考查了一元一次不等式組的解法，解決此類問題的關(guān)鍵在于正確解得不等式組或不等式的解集，然后再根據(jù)題目中對于解集的限制得到下一步所需要的條件，再根據(jù)得到的條件進而求得不等式組的整數(shù)解．三、板書設(shè)計一元一次不等式組概念解法不等式組的解集利用數(shù)軸確定解集利用口訣確定解集解一元一次不等式組是建立在解一元一次不等式的基礎(chǔ)之上．解不等式組時，先解每一個不等式，再確定各個不等式組的解集的公共部分.
北師大初中八年級數(shù)學(xué)下冊一元一次不等式的應(yīng)用教案
有三種購買方案：購A型0臺，B型10臺；A型1臺，B型9臺；A型2臺，B型8臺；(2)240x＋200(10－x)≥2040，解得x≥1，∴x為1或2.當x＝1時，購買資金為12×1＋10×9＝102(萬元)；當x＝2時，購買資金為12×2＋10×8＝104(萬元)．答：為了節(jié)約資金，應(yīng)選購A型1臺，B型9臺．方法總結(jié)：此題將現(xiàn)實生活中的事件與數(shù)學(xué)思想聯(lián)系起來，屬于最優(yōu)化問題，在確定最優(yōu)方案時，應(yīng)把幾種情況進行比較．三、板書設(shè)計應(yīng)用一元一次不等式解決實際問題的步驟：實際問題――→找出不等關(guān)系設(shè)未知數(shù)列不等式―→解不等式―→結(jié)合實際問題確定答案本節(jié)課通過實例引入，激發(fā)學(xué)生的學(xué)習(xí)興趣，讓學(xué)生積極參與，講練結(jié)合，引導(dǎo)學(xué)生找不等關(guān)系列不等式．在教學(xué)過程中，可通過類比列一元一次方程解決實際問題的方法來學(xué)習(xí)，讓學(xué)生認識到列方程與列不等式的區(qū)別與聯(lián)系.
北師大初中八年級數(shù)學(xué)下冊一元一次不等式的解法教案
方法總結(jié)：已知解集求字母系數(shù)的值，通常是先解含有字母的不等式，再利用解集唯一性列方程求字母的值．解題過程體現(xiàn)了方程思想．三、板書設(shè)計1．一元一次不等式的概念2．解一元一次不等式的基本步驟：(1)去分母；(2)去括號；(3)移項；(4)合并同類項；(5)兩邊都除以未知數(shù)的系數(shù)．本節(jié)課通過類比一元一次方程的解法得到一元一次不等式的解法，讓學(xué)生感受到解一元一次不等式與解一元一次方程只是在兩邊都除以未知數(shù)的系數(shù)這一步時有所不同．如果這個系數(shù)是正數(shù)，不等號的方向不變；如果這個系數(shù)是負數(shù)，不等號的方向改變．這也是這節(jié)課學(xué)生容易出錯的地方．教學(xué)時要大膽放手，不要怕學(xué)生出錯，通過學(xué)生犯的錯誤引起學(xué)生注意，理解產(chǎn)生錯誤的原因，以便在以后的學(xué)習(xí)中避免出錯.
北師大初中八年級數(shù)學(xué)下冊一元一次不等式組的解法及應(yīng)用教案
安裝及運輸費用為600x＋800(12－x)，根據(jù)題意得4000x＋3000（12－x）≤40000，600x＋800（12－x）≤9200.解得2≤x≤4，由于x取整數(shù)，所以x＝2，3，4.答：有三種方案：①購買甲種設(shè)備2臺，乙種設(shè)備10臺；②購買甲種設(shè)備3臺，乙種設(shè)備9臺；③購買甲種設(shè)備4臺，乙種設(shè)備8臺．方法總結(jié)：列不等式組解應(yīng)用題時，一般只設(shè)一個未知數(shù)，找出兩個或兩個以上的不等關(guān)系，相應(yīng)地列出兩個或兩個以上的不等式組成不等式組求解．在實際問題中，大部分情況下應(yīng)求整數(shù)解．三、板書設(shè)計1．一元一次不等式組的解法2．一元一次不等式組的實際應(yīng)用利用一元一次不等式組解應(yīng)用題關(guān)鍵是找出所有可能表達題意的不等關(guān)系，再根據(jù)各個不等關(guān)系列成相應(yīng)的不等式，組成不等式組．在教學(xué)時要讓學(xué)生養(yǎng)成檢驗的習(xí)慣，感受運用數(shù)學(xué)知識解決問題的過程，提高實際操作能力.
北師大初中數(shù)學(xué)八年級上冊二次根式的混合運算2教案
本節(jié)課開始時，首先由一個要在一塊長方形木板上截出兩塊面積不等的正方形，引導(dǎo)學(xué)生得出兩個二次根式求和的運算。從而提出問題：如何進行二次根式的加減運算?這樣通過問題指向本課研究的重點，激發(fā)學(xué)生的學(xué)習(xí)興趣和強烈的求知欲望。本節(jié)課是二次根式加減法，目的是探索二次根式加減法運算法則，在設(shè)計本課時教案時，著重從以下幾點考慮：1.先通過對實際問題的解決來引入二次根式的加減運算，再由學(xué)生自主討論并總結(jié)二次根式的加減運算法則。2.四人小組探索、發(fā)現(xiàn)、解決問題，培養(yǎng)學(xué)生用數(shù)學(xué)方法解決實際問題的能力。3.對法則的教學(xué)與整式的加減比較學(xué)習(xí)。在理解、掌握和運用二次根式的加減法運算法則的學(xué)習(xí)過程中，滲透了分析、概括、類比等數(shù)學(xué)思想方法，提高學(xué)生的思維品質(zhì)和興趣。
北師大初中數(shù)學(xué)八年級上冊二次根式的運算1教案
1．會用二次根式的四則運算法則進行簡單地運算；(重點)2．靈活運用二次根式的乘法公式．(難點)一、情境導(dǎo)入下面正方形的邊長分別是多少？這兩個數(shù)之間有什么關(guān)系，你能借助什么運算法則或運算律解釋它？二、合作探究探究點一：二次根式的乘除運算【類型一】 二次根式的乘法計算：(1)3×5； (2)13×27；(3)2xy×1x； (4)14×7.解：(1)3×5＝15；(2)13×27＝13×27＝9＝3；(3)2xy×1x＝2xy×1x＝2y；(4)14×7＝14×7＝72×2＝72.方法總結(jié)：幾個二次根式相乘，把它們的被開方數(shù)相乘，根指數(shù)不變，如果積含有能開得盡方的因數(shù)或因式，一定要化簡．【類型二】 二次根式的除法計算a2－2a÷a的結(jié)果是()A.－a－2 B．－－a－2C.a－2 D．－a－2解析：原式＝a2－2aa＝a（a－2）a＝a－2.故選C.
北師大初中數(shù)學(xué)八年級上冊二次根式的運算2教案
1．關(guān)于二次根式的概念，要注意以下幾點：（1）從形式上看，二次根式是以根號“ ”表示的代數(shù)式，這里的開方運算是最后一步運算。如 ， 等不是二次根式，而是含有二次根式的代數(shù)式或二次根式的運算；（2）當一個二次根式前面乘有一個有理數(shù)或有理式（整式或分式）時，雖然最后運算不是開方而是乘法，但為了方便起見，我們把它看作一個整體仍叫做二次根式，而前面與其相乘的有理數(shù)或有理式就叫做二次根式的系數(shù)；（3）二次根式的被開方數(shù)，可以是某個確定的非負實數(shù)，也可以是某個代數(shù)式表示的數(shù)，但其中所含字母的取值必須使得該代數(shù)式的值為非負實數(shù)；（4）像“ ， ”等雖然可以進行開方運算，但它們?nèi)詫儆诙胃健?．二次根式的主要性質(zhì)（1） ； （2） ； （3） ；（4）積的算術(shù)平方根的性質(zhì)： ；（5）商的算術(shù)平方根的性質(zhì)： ；