document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=30251>Question 30251</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Is each a function? Explain<BR>\n" );
document.write( "1. {(1,9), (9,-1), (-1,8), (-9,1)}\r<BR>\n" );
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document.write( "2. {(2,5), (-2,4), (3,-8), (-2,7), (-1,4)} </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #17024 by </B><A HREF=/tutors/aboutme.mpl?userid=mukhopadhyay><B>mukhopadhyay(490)</B></A><img src=\"/images/stars/stars-10.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=mukhopadhyay><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=17024\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Based on the definition of a function, there cannot be more than one f(x) value for the same x;\r<BR>\n" );
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document.write( "In example 1, Since x value is not duplicated (possible values of x are  1, 9, -1, and -9), the situation of more than one f(x) for the same x does not arise and hence it is a function.\r<BR>\n" );
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document.write( "In example 2, x value duplicates in {-2,4), {-2,7}).  For x = -2, the values of f(x) are 4 and 7;  So, this is not a function. </SPAN>\n" );
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