高中考试数学专题复习之函数的定义域与值域演示课件.ppt

《函数的定义域》 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 一、由函数解析式求定义域 明晰函数的约束条件→细致 非空 数集 求下列函数的定义域： 1、 y=lg(4x+3) 2、y=1/lg(4x+3) 3、y=(5x-4)0 4、y=x2/lg(4x+3)+(5x-4)0 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 5、用长为l的铁丝弯成下部的矩形，上部分为半圆的框架（如图），若矩形的底边长为2x，求此框架围成面积y与x的函数，写出的定义域。 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 二、由y=f(x)的定义域，求复合函数y=f(g(x))的定义域；或者反过来。 例2、设函数f(x)的定义域为[-2，9），求下列函数的定义域： 1) f(x+2) 2) f(3x) 3) f(x2) 4) f(lgx+5) 5) g(x)=f(-x)+f(x) 实质：已知中间变量u=g(X)的值域， 求x的 范围。 练习：已知函数f(x)的定义域为［－1,1），则F(x)=f(1―x)+f(1―x2)的定义域为＿＿。 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 例4、已知函数f(x)=1/(x+1)，则f[f(x)]的定义域为_____ 例3、函数f(2x)的定义域是［－1,1］，则f(log2x)的定义域为______ Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 例8、若函数y=lg(4－a?2x)的定义域为R， 则实数a的取值范围是_______ 三：定义域为R的数学问题 等价于对于一切实数恒成立问题 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 综合3： 已知函数f(x)=lg(mx2－4mx+m+3) 1）若f(x)的定义域为R，则实数m的取值范围是_______ 2）若f(x)的值域为R，则实数m的取值范围___________ Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 课堂回顾： 求定义域的几种类型： 一类重要的数学问题： Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.