document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=312082>Question 312082</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A rock is thrown from the top of a tall building.  The distance, d, in feet, between the rock and the ground t seconds after it is thrown is given by the model\r<BR>\n" );
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document.write( "d=-16t^2-2t+524\r<BR>\n" );
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document.write( "How long after the rock is thrown is it 321 feet from the ground? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #223127 by </B><A HREF=/tutors/aboutme.mpl?userid=solver91311><B>solver91311(24713)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=solver91311><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=solver91311><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=223127\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <font face=\"Garamond\" size=\"+2\">\r<BR>\n" );
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document.write( "We are given that\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=\"/cgi-bin/rendertex.cgi?\LARGE \ \ \ \ \ \ \ \ \ \ d\ =\ -16t^2\ -\ 2t\ +\ 524\">\r<BR>\n" );
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document.write( "So we are at the top of a 524 foot tall building throwing a rock downward with an initial velocity of 2 feet per second toward the ground.\r<BR>\n" );
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document.write( "But we want to know the time when\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=\"/cgi-bin/rendertex.cgi?\LARGE \ \ \ \ \ \ \ \ \ \ d\ =\ 321\"> feet.\r<BR>\n" );
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document.write( "Set the two expressions equal to each other because they are both equal to  <IMG STYLE=\"max-width:80%;\" SRC=\"/cgi-bin/rendertex.cgi?\LARGE d\">.\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=\"/cgi-bin/rendertex.cgi?\LARGE \ \ \ \ \ \ \ \ \ \ -16t^2\ -\ 2t\ +\ 524\ =\ 321\">\r<BR>\n" );
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document.write( "Which is to say:\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=\"/cgi-bin/rendertex.cgi?\LARGE \ \ \ \ \ \ \ \ \ \ -16t^2\ -\ 2t\ +\ 203\ =\ 0\">\r<BR>\n" );
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document.write( "Just solve the quadratic for <IMG STYLE=\"max-width:80%;\" SRC=\"/cgi-bin/rendertex.cgi?\LARGE t\">.  Hint:  The quadratic factors because 2 times -8 is -16, (-8 times -7) plus (2 times -29)\ = 56 minus 58 = minus 2, and -7 times -29 is 203.\r<BR>\n" );
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document.write( "One of the roots is negative -- discard it.  You don't care what happened <b><i>before</i></b> you threw the rock.  The positive root is the number of seconds that will have elapsed when the height of the rock is 321 feet. \r<BR>\n" );
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document.write( "John<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=\"/cgi-bin/rendertex.cgi?\LARGE e^{i\pi} + 1 = 0\"><BR>\n" );
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