document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1018207>Question 1018207</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A(-2,1) B(4,4) C(6,1) D(4,-2) are the vertices of a kite. Prove that BD is perpendicular to AC.\r<BR>\n" );
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document.write( "I found the gradients are both equal to 0, so are they still perpendicular? Don't both the gradients have to be equal to -1? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #634381 by </B><A HREF=/tutors/aboutme.mpl?userid=FrankM><B>FrankM(1040)</B></A><img src=\"/images/stars/stars-12.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=FrankM><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=FrankM><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=634381\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <IMG STYLE=\"max-width:80%;\" SRC=\"/cgi-bin/display-illustration.mpl?tutor=FrankM&illustration_name=Screen_shot_2016_02_06_at_7.50.13_AM.png\">\r<BR>\n" );
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document.write( "This should make it clear. BD has an undefined slope, i.e. a denominator of 0. AC has 0 slope. These are perpendicular.  </SPAN>\n" );
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