1、21.1二次根式Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.學(xué)習(xí)目標(biāo)：（1）二次根式的概念（2）根號內(nèi)字母的取值范圍（3）二次根式的性質(zhì)Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.復(fù)習(xí)1、如果 ，那么 ；2、如果 ，那么 ；3、如果

2、 ，那么 。2Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.50米a米 塔座所形成的這個(gè)直角三角形的斜邊長為_米。塔座?米Evaluation only.Created with Aspos

3、e.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.下球體S 圓形的下球體在平面圖上的面積為S，則半徑為_.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd. 如圖示的值表示正方形的面積，則正方形的邊長是b-3表示一些正數(shù)的算術(shù)平方根a叫被開方數(shù)Evaluation only.Created with Aspos

4、e.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.憑著你已有的知識,說說對二次根式 的認(rèn)識,好嗎? ?開動你的腦筋,你一定行!Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.2. a可以是數(shù),也可以是式子.3. 形式上含有二次根號4. a0, 0 5.既可表示開方運(yùn)算,也可表示運(yùn)算的結(jié)果.1.表示a的算術(shù)平方

5、根( 雙重非負(fù)性)Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.說一說: 下列各式是二次根式嗎? ?(m0),(x,y 異號)注意：在實(shí)數(shù)范圍內(nèi),負(fù)數(shù)沒有平方根火眼金睛Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.(1) (2)(3)

6、解：由 得解：由 得(a為任何實(shí)數(shù))例1 a取何值時(shí),下列根式有意義?Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.(3)總結(jié):被開方數(shù)不小于零；變式：(1)(2)(a為任何實(shí)數(shù))(a=1)Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.

7、例1 x取何值時(shí),下列二次根式有意義?你有什么收獲？ 被開方數(shù)大于等于零；分母中有字母時(shí)，要保證分母不為零。Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.魔幻水晶球你能用魔法師變出的這些代數(shù)式作為被開方數(shù)構(gòu)造二次根式嗎？3-23-2Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019

8、-2019 Aspose Pty Ltd.練:利用算術(shù)平方根的意義填空:(a0)040.0140.010(a0)觀測上述等式的兩邊,你能得到什么啟示? ?Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.合作探究:Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspos

9、e Pty Ltd.計(jì)算：5Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.2.從取值范圍來看, a0a取任何實(shí)數(shù)1:從運(yùn)算順序來看,先開方,后平方先平方,后開方區(qū)別:區(qū)別Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.3.從運(yùn)算結(jié)果來看:

10、=aa (a 0)-a (a0)=aEvaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.代數(shù)式歸納Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.例3:12-a+b+c-（b-a+c)=-a+b+c-b+a-c=0Evaluation only

11、.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.練習(xí):用心算一算:5718(xy)Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.化簡下列各式:=18+12=30=5+5=10=8-m=-abEvaluation only.Created with Aspose.Sli

12、des for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.能力小測驗(yàn)已知a.b為實(shí)數(shù)，且滿足 求a 的值.2b-10,1-2b 0.2b-1=0,即b=1/2.a=1注意：如果互為相反數(shù)的兩個(gè)數(shù)同時(shí)作為被開方數(shù)時(shí)，那么它等于零.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.已知 有意義,那A(a, )在 象限.二 ?試試你的

13、反應(yīng)由題意知a0點(diǎn)A(,)知識縱橫Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.試試你的反應(yīng) ?2x+60-2x0 x-3x0知識縱橫Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.因?yàn)殡y,所以我挑戰(zhàn)!Evaluation only.Cr

14、eated with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.鞏固當(dāng)t是怎樣的實(shí)數(shù)時(shí)， 有最小值？最小值是多少？Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd. ?若a.b為實(shí)數(shù),且求 的值解: 試試你的反應(yīng)知識縱橫Evaluation only.Created with Aspose.S

15、lides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.點(diǎn)擊中考:實(shí)數(shù)p在數(shù)軸上的位置如圖所示，化簡 Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.在實(shí)數(shù)范圍內(nèi)分解因式:4 - 3 ?試試你的反應(yīng)解:Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.碩果累累 一路下來，我們結(jié)識了很多新知識，你能談?wù)勛约旱氖斋@嗎？說一說，讓大家一起來分享。Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile .Copyright 2019-2019 Aspose Pty Ltd.二次根式的定義:二次根式的性質(zhì):a (a