Algebra.Com's Answer #91867 by solver91311(24713)![\"\"](\"/images/stars/stars-13.gif\")  
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A value is in the domain of a function if and only if the function is defined for that value of the independent variable.\r
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document.write( "For example:\r
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document.write( "1.  . You can substitute any real number for x and the function will be defined. So the domain is all real numbers.\r
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document.write( "2.  . Here, to be defined in the real number system, x cannot be less than zero, so the domain is all positive real numbers and zero. Using set notation you would say {x | x is real,  }. On the other hand, if the function were defined in the complex number system, there would be no restriction on the domain.\r
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document.write( "3.  . A value cannot be in the domain of a function if that value causes any denominator in the function to be zero. Here, 3 or -3 would make the denominator zero, and therefore need to be excluded from the domain which is otherwise all real numbers. In interval notation:\r
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document.write( "( , ) U (, ) U (, ). The parentheses rather than brackets indicate that the endpoints are not included and the U indicates that you want the union of the three intervals. \n" );
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