document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=344469>Question 344469</A>: <I><SPAN STYLE=\"word-break: break-all;\"> a ball is thrown upward with an initial velocity of 96ft/s from a height 640ft. h = -16t^2 + 96t + 640. After how many seconds will the ball reach 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 #246423 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=246423\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> h = -16t^2 + 96t + 640<BR>\n" );
document.write( "since h is height, set it to zero and solve for t:<BR>\n" );
document.write( "0 = -16t^2 + 96t + 640<BR>\n" );
document.write( "Dividing both sides by -16:<BR>\n" );
document.write( "0 = t^2 - 6t - 40<BR>\n" );
document.write( "0 = (t-10)(t+4)<BR>\n" );
document.write( ".<BR>\n" );
document.write( "t = {-4, 10}<BR>\n" );
document.write( "we can toss out the negative solution leaving:<BR>\n" );
document.write( "t = 10 seconds<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );