青岛版八年级数学二次根式课件说课材料.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,二 次 根 式,东明中学,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,请你凭着自己已有的知识和记忆,说说对 的认识！,?,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,1.,读作根号a,2.,表示a的算术平方根,3.,a0,0,形如 ()的式子叫做二次根式,。,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,知识点1 二次根式的概念,a叫,被开方数，,称为二次根号,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,举出几个二次根式的例子：如：,，,，,，,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,说一说:,例1.下列各式是二次根式吗?,(m0),(x,y 异号),在实数范围内,负数没有平方根,火眼金睛,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,思考：,若,是二次根式，则字母x需要满足什么条件呢？,强调：,要保证二次根式有意义，就要使根号下的数大于等于0。,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,例2、x,是怎样的实数时，下列各式在实数范围,内有意义？,（1）,（2）,解：（1）要使 在实数范围内有意义,则x-3 0,解得x 3,当x 3时，在实数范围内有意义,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,（2）,解：要使 在实数范围内有意义,则,1-0,x0,解得x0且x1,当x0且x1时，在实数范围内有意义,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,练习2：,x取何值时，下列各式在实数范围内有意义？,（1）（2）,（3）（4）,（,5,）,+,快速口答,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,练习,3,：若,+=0,，求,a,、,b,的值。,解：（x+2),2,0，0，（x+2）,2,+=0,（x+2),2,=0，=0,解得x=-2 y=0,x,y,=(-2),0,=1,例3：已知（x+2）,2,+=0，求,x,y,=？,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,知识点2 二次根式的性质,1.a0,0,(双重非负性),Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,a=1,b=7,求a,b的值,已知,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,例4.根据算术平方根的意义填空：,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,知识点2 二次根式的性质,2.,(a0),Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,二次根式的简单性质,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,例如：,3=（),2,，,b=（),2,（,b 0,）,知识点3.性质公式 的逆用,利用这个式子，可以把任何一个非负数写 成一个数的平方的形式。,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,?,试试你的反应,例5：在 范围内因式分解：,解：,练习5：在实数范围内因式分解,（1）（2）,实数,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,梳理一下吧,（1）二次根式的概念,（2）二次根式的性质,a0,0,(a0),Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,2、求下列二次根式中字母的取值范围：,当堂达标,（1）（2）,3.已知,，求,的值.,1、（1）,（2）,已知 有意义,那A(,a,)在,象限.,80,二,9,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,拓展延伸:,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,谢谢观摩！,Evaluation only.,Created with Aspose.Slides for.NET 3.5 Client Profile 5.2.0.0.,Copyright 2004-2011 Aspose Pty Ltd.,