document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1179995>Question 1179995</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The four vertices of a quadrilateral are A (-4,5), B(1,9), C(6,5) and D(1,1). Can you help me prove the quadrilateral is a rhombus ?  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #809556 by </B><A HREF=/tutors/aboutme.mpl?userid=Boreal><B>Boreal(15235)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Boreal><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=Boreal><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=809556\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Need to show sides are equal and parallel.<BR>\n" );
document.write( "Distance AB is sqrt ((diff x)^2+ (diff y)^2)=sqrt (41)<BR>\n" );
document.write( "BC is also sqrt (41)<BR>\n" );
document.write( "so are the other two sides. So sides have equal length.\r<BR>\n" );
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document.write( "Now show that AB and CD are parallel, by showing slopes are equal and BC and DA have equal slopes.<BR>\n" );
document.write( "slope is (diff y)/(diff x) or (4/5) for AB; (-4/5) for BC; (4/5) for CD; and (-4/5) for BA.<BR>\n" );
document.write( "They are parallel.<BR>\n" );
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