document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=941528>Question 941528</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I am having trouble setting up the quadratic equation from this word problem.\r<BR>\n" );
document.write( "\n" );
document.write( "A missile fired straight up into the air has a height, in meters, given by h=-5t^2+15t, where t is the time, in seconds, the missle has been in the air. By setting up and solving an equation, find the time when the missle hits the ground.\r<BR>\n" );
document.write( "\n" );
document.write( "after_____seconds<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #573943 by </B><A HREF=/tutors/aboutme.mpl?userid=nerdybill><B>nerdybill(7384)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=nerdybill><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=nerdybill><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=573943\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A missile fired straight up into the air has a height, in meters, given by h=-5t^2+15t, where t is the time, in seconds, the missle has been in the air. By setting up and solving an equation, find the time when the missle hits the ground.<BR>\n" );
document.write( "after_____seconds<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Since\"h\" is the height, when the missile hits the ground, h should be zero.<BR>\n" );
document.write( "Our equation:<BR>\n" );
document.write( "0 = -5t^2+15t<BR>\n" );
document.write( "factor the right<BR>\n" );
document.write( "0 = (-5t)(t-3)<BR>\n" );
document.write( "t = {0, 3}<BR>\n" );
document.write( "throw out the 0, this represents when the missile was fired.<BR>\n" );
document.write( "Answer: 3 seconds </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );