document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1091375>Question 1091375</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Show that point (0,-1),(6,7),(-2,3),(8,3) are vertics of rectangle </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #705820 by </B><A HREF=/tutors/aboutme.mpl?userid=greenestamps><B>greenestamps(13200)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=greenestamps><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=greenestamps><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=705820\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <br>Call the quadrilateral ABCD, with A(0,-1), B(-2,3), C(6,7), and D(8,3).  The quadrilateral is a rectangle if all the angles are right angles; the angles are right angles if adjacent sides are perpendicular to each other; adjacent sides are perpendicular to each other if their slopes are negative reciprocals.<br><BR>\n" );
document.write( "So find the slope of each side of the quadrilateral.  I think drawing a sketch is easier (and less prone to careless errors) than using the formula for the slope of a line segment between two points.<br><BR>\n" );
document.write( "The slope of AB is -2; the slope of BC is 1/2.  Since (-2)(1/2) = -1, AB and BC are perpendicular.<br><BR>\n" );
document.write( "Find the slopes of CD and DA to finish showing that the figure is a rectangle. </SPAN>\n" );
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