document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=65746>Question 65746</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A ball is thrown upward from the roof of a building 100m tall with an initial velocity of 10m/s. When will the ball reach a hieght of 80m?\r<BR>\n" );
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document.write( "Same thing I can not understand how to solve this type of problem, thank you so much for the help:-) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #46460 by </B><A HREF=/tutors/aboutme.mpl?userid=Nate><B>Nate(3500)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Nate><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=46460\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> f(t) = at^2 + bt + c<BR>\n" );
document.write( "a = -16<BR>\n" );
document.write( "b = speed<BR>\n" );
document.write( "c = height<BR>\n" );
document.write( "t = time<BR>\n" );
document.write( "f(t) = height after a unit of time (t)<BR>\n" );
document.write( "80 = -16t^2 + 10t + 100<BR>\n" );
document.write( "-20 = -16t^2 + 10t<BR>\n" );
document.write( "20/16 = t^2 - 10t/16<BR>\n" );
document.write( "20/16 = t^2 - 5t/8<BR>\n" );
document.write( "20/16 + 25/16^2 = (t - 5/16)^2<BR>\n" );
document.write( "320/16^2 + 25/16^2 = 345/16^2 = (t - 5/16)^2<BR>\n" );
document.write( "+- sqrt(345)/16 = t - 5/16<BR>\n" );
document.write( "5/16 +- sqrt(345)/16 = t<BR>\n" );
document.write( "After about 1.4734 seconds, the ball will reach 80m. </SPAN>\n" );
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