document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1021050>Question 1021050</A>: <I><SPAN STYLE=\"word-break: break-all;\"> quadrilateral abcd has vertices a(-3 2) b(-1 5) c(5 1) and d(3 -2). prove that abcd is a rectangle </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #636913 by </B><A HREF=/tutors/aboutme.mpl?userid=robertb><B>robertb(5830)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=robertb><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/cgi-bin/show-face.mpl?user=robertb><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=636913\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Line AB has slope <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=m%5BAB%5D+=+%285-2%29%2F%28-1%2B3%29+=+3%2F2 ALIGN=MIDDLE  ALT=\"m%5BAB%5D+=+%285-2%29%2F%28-1%2B3%29+=+3%2F2\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Line CD has slope <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=m%5BCD%5D+=+%281%2B2%29%2F%285-3%29+=+3%2F2 ALIGN=MIDDLE  ALT=\"m%5BCD%5D+=+%281%2B2%29%2F%285-3%29+=+3%2F2\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "==> Lines AB and CD are parallel.\r<BR>\n" );
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document.write( "Line BC has slope <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=m%5BBC%5D+=+%285-1%29%2F%28-1-5%29+=+-2%2F3 ALIGN=MIDDLE  ALT=\"m%5BBC%5D+=+%285-1%29%2F%28-1-5%29+=+-2%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Line AD has slope <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=m%5BAD%5D+=+%282%2B2%29%2F%28-3-3%29+=+-2%2F3 ALIGN=MIDDLE  ALT=\"m%5BAD%5D+=+%282%2B2%29%2F%28-3-3%29+=+-2%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "==> Lines BC and AD are parallel.\r<BR>\n" );
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document.write( "Last thing is to just show that one of the four angles is a right angle. <BR>\n" );
document.write( "Since the slope of line AB, 3/2, and the slope of line CD, -2/3, have a product of -1, it follows that the angle at vertex C is a right angle, and the proof is complete. </SPAN>\n" );
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