document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=908390>Question 908390</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A fireworks shell is shot straight up with an initial velocity of 80 feet per second. Its height s after t seconds is given by the equation <BR>\n" );
document.write( "s = 80t &#8722; 16t2.<BR>\n" );
document.write( " If the shell is designed to explode when it reaches its maximum height, how long after being fired, and at what height, will the fireworks appear in the sky?\r<BR>\n" );
document.write( "\n" );
document.write( "time=_______ sec<BR>\n" );
document.write( "height=_________ft </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #551009 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=551009\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Its height s after t seconds is given by the equation s = 80t &#8722; 16t^2.<BR>\n" );
document.write( "If the shell is designed to explode when it reaches its maximum height, how long after being fired?<BR>\n" );
document.write( "-----<BR>\n" );
document.write( "Max occurs when x = -b/(2a) = -80/(2*-16) = 5/2 seconds<BR>\n" );
document.write( "---------<BR>\n" );
document.write( "And at what height, will the fireworks appear in the sky?<BR>\n" );
document.write( "f(5/2) = 80(5/2) - 16(5/2)^2 = 200 - 20 = 180 ft<BR>\n" );
document.write( "============================<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
document.write( "-------------------<BR>\n" );
document.write( "  </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );