document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=992241>Question 992241</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A person standing close to the edge on the top of a 270-foot building throws a baseball vertically upward. The quadratic equation\r<BR>\n" );
document.write( "\n" );
document.write( "\qquad\qquad h = -16 t^2 + 160 t + 270\r<BR>\n" );
document.write( "\n" );
document.write( "models the ball's height \, h \, above the ground in feet, t seconds after it was thrown.\r<BR>\n" );
document.write( "\n" );
document.write( "How high is the ball after 5 seconds?\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( " ??feet.\r<BR>\n" );
document.write( "\n" );
document.write( "How many seconds does it take until the ball finally hits the ground? Round to the nearest tenth of a second.\r<BR>\n" );
document.write( "\n" );
document.write( "?? seconds.<BR>\n" );
document.write( "(I plugged in 5, then set it equal to 0, none of it worked, I'm probably doing it wrong) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #611959 by </B><A HREF=/tutors/aboutme.mpl?userid=rothauserc><B>rothauserc(4718)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=rothauserc><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=rothauserc><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=611959\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> h = -16 t^2 + 160 t + 270 <BR>\n" );
document.write( "to find the height of the ball after 5 seconds substitute 5 for t<BR>\n" );
document.write( "h = -16(5^2) + (160*5) + 270<BR>\n" );
document.write( "h =  670 feet high after 5 seconds<BR>\n" );
document.write( "*****************************************************************<BR>\n" );
document.write( "to find when the ball hits the ground, set h = 0 and solve the quadratic for t<BR>\n" );
document.write( "-16 t^2 + 160 t + 270 = 0<BR>\n" );
document.write( "multiply both sides of = by -1<BR>\n" );
document.write( "16t^2 - 160t - 270 = 0<BR>\n" );
document.write( "use quadratic formula to solve for t<BR>\n" );
document.write( "t = (160 + sqrt(160^2 - (4*16*(-270)))) / (2*16) = 11.471089553 approx 11.5<BR>\n" );
document.write( "t = (160 - sqrt(160^2 - (4*16*(-270)))) / (2*16) = &#8722;1.471089553 approx -1.5<BR>\n" );
document.write( "****************************************************************************<BR>\n" );
document.write( "we want the positive value for t<BR>\n" );
document.write( "t = 11.5 seconds for the ball to hit the ground<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );