document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=83167>Question 83167</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Which of the folowing are the pair of equations whose graphs are not perpendicular?\r<BR>\n" );
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document.write( "A. 2x-8y=9<BR>\n" );
document.write( "  12x-3y=7\r<BR>\n" );
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document.write( "B.3x+6y=8<BR>\n" );
document.write( "   y=2x-8\r<BR>\n" );
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document.write( "C.y=x-7<BR>\n" );
document.write( "  x+y=3\r<BR>\n" );
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document.write( "D. 2y=3x+5<BR>\n" );
document.write( "   2x+3y=4 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #59681 by </B><A HREF=/tutors/aboutme.mpl?userid=Mona27><B>Mona27(45)</B></A><img src=\"/images/stars/stars-07.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Mona27><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=59681\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> It's the first one (A)<BR>\n" );
document.write( "That's because the product of the gradients (slopes) of two perpendicular lines must be -1.\r<BR>\n" );
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document.write( "In the first case:<BR>\n" );
document.write( "the gradient of the first line = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%2F8=1%2F4 ALIGN=MIDDLE  ALT=\"2%2F8=1%2F4\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "and the gradient of the second line = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12%2F3=4 ALIGN=MIDDLE  ALT=\"12%2F3=4\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "since both gradients are positive then they cannot give a product of -1, and therefore are not perpendicular. </SPAN>\n" );
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