document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=91415>Question 91415</A>: <I><SPAN STYLE=\"word-break: break-all;\"> What is the slope and the y-intercept of x= -9? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #66381 by </B><A HREF=/tutors/aboutme.mpl?userid=bucky><B>bucky(2189)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=bucky><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=66381\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The graph of this equation [ x = -9] is a vertical line through -9 on the x-axis.<BR>\n" );
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document.write( "[Think of it this way ... x is always -9 no matter what y is. Therefore, (-9,-10), (-9, 0), <BR>\n" );
document.write( "(-9, 26) are all points on the graph. They all have x = -9 and therefore they all satisfy<BR>\n" );
document.write( "the given equation x = -9.]<BR>\n" );
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document.write( "Because the graph of this equation is a vertical line, it is parallel to the y-axis.<BR>\n" );
document.write( "Therefore, there is no y-intercept.  Do not say that the y intercept is zero. That is incorrect<BR>\n" );
document.write( "because it does not mean the same as there IS NO y-intercept.<BR>\n" );
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document.write( "The slope of this vertical line graph is undefined. Why is that? Slope is defined as:<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+Slope+=+Rise%2FRun ALIGN=MIDDLE  ALT=\"+Slope+=+Rise%2FRun\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "But the Run (the horizontal change) is zero.  Therefore the Slope equation becomes:<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=Slope+=+Rise%2F0 ALIGN=MIDDLE  ALT=\"Slope+=+Rise%2F0\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "But division by zero is not allowed in algebra.  Therefore, the slope is undefined.<BR>\n" );
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document.write( "Also note that an undefined slope is NOT the same as a slope equal to zero.  A line that<BR>\n" );
document.write( "has a zero slope is a horizontal line, not a vertical line.<BR>\n" );
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document.write( "Hope this helps you to understand the problem a little better.<BR>\n" );
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