document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1400>Question 1400</A>: <I><SPAN STYLE=\"word-break: break-all;\"> 1. How do you take a graph and generate an equation from it?\r<BR>\n" );
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document.write( "2. When comparing two linear equations, how can I tell if the corresponding lines are parallel? How can I tell if they are perpendicular? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #454 by </B><A HREF=/tutors/aboutme.mpl?userid=khwang><B>khwang(438)</B></A><img src=\"/images/stars/stars-10.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=khwang><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=454\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\">  Given a system of two linear equations:\r<BR>\n" );
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document.write( " a1 x + b1 y = c1...(1),\r<BR>\n" );
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document.write( " a2 x + b2 y = c2...(2)\r<BR>\n" );
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document.write( " slope of (1): m1 = -a1/b1 (if b1 <> 0)\r<BR>\n" );
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document.write( " slope of (1): m2 = -a2/b2 (if b2 <> 0)\r<BR>\n" );
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document.write( " if a1/b1 = a2/b2 (same solpe) but is not equal to c1/c2 then the two lines<BR>\n" );
document.write( " are parallel\r<BR>\n" );
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document.write( " if a1/b1 * a2/b2 = -1 (ie a1a2 = -b1b2 ) then the two lines<BR>\n" );
document.write( " are perpendicular.\r<BR>\n" );
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document.write( " Try to think when b1 or b2 = 0  </SPAN>\n" );
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