document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=235802>Question 235802</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Which of the following are functions?  \r<BR>\n" );
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document.write( "a. f(x) = x + 4\r<BR>\n" );
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document.write( "b. f(x) = 3 if x>2 otherwise f(x) = -2\r<BR>\n" );
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document.write( "c. f(x) = 7 if x>0 or f(x) = -7 if x<0 or f(x) = 7 or -7 if x = 0\r<BR>\n" );
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document.write( "I believe A is a function but that B and C are not, but I am not sure.  How do I tell?  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #173708 by </B><A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><B>jim_thompson5910(35256)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><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=173708\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A and B are both functions since they pass the vertical line test (plot them out to verify). However, C is not a function since if x=0, then f(x)=7 or -7. Remember, a relation is a function only if each input has exactly one output. Since the input of x=0 produces two outputs, this means C is not a function. </SPAN>\n" );
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