document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=762367>Question 762367</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I stand on a building 640 feet high and throw a rock into the air with a velocity of 96 ft/sec. When does the rock have a height of 800 feet?  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #463900 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=463900\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\">  I stand on a building 640 feet high and throw a rock into the air with a velocity of 96 ft/sec. When does the rock have a height of 800 feet? <BR>\n" );
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document.write( "h(t) = -16t^2 + 96t + 640<BR>\n" );
document.write( "------<BR>\n" );
document.write( "Solve:<BR>\n" );
document.write( "-16t^2 + 96t + 640 = 800<BR>\n" );
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document.write( "-16t^2 + 96t - 160 = 0<BR>\n" );
document.write( "----<BR>\n" );
document.write( "-16(t^2 - 6t + 10) = 0<BR>\n" );
document.write( "---<BR>\n" );
document.write( "Quadratic formula:<BR>\n" );
document.write( "t = [6 +- sqrt(36-4*10)]/(2)<BR>\n" );
document.write( "----<BR>\n" );
document.write( "Since 36-4*10 is negative there is no Real Number solution.<BR>\n" );
document.write( "---<BR>\n" );
document.write( "The rock never teaches a height of 800 ft.<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
document.write( "============== </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );