document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1028630>Question 1028630</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A football is kicked into the air. The height of the football is modelled by h(t)=-5t^2+16t+1 when the height is in metres and t is the time in seconds from its release. When will the football first reach the height of 13 metres? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #643730 by </B><A HREF=/tutors/aboutme.mpl?userid=Natolino1983><B>Natolino1983(23)</B></A><img src=\"/images/stars/stars-07.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Natolino1983><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=643730\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> H(t) = -5×t^2 +16×t + 1 = 13, where t>=0\r<BR>\n" );
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document.write( "         5×t^2 -16×t + 12 =0<BR>\n" );
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document.write( "         t= (16 +/- sqrt (16^2 -4×5×12))/(2×5)\r<BR>\n" );
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document.write( "         t= (16+/-4)/10 \r<BR>\n" );
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document.write( "         t= 2 (s) or t = 1,2 (s)\r<BR>\n" );
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document.write( "So the minimum(first reach) time is 1,2 (s) after the kick. </SPAN>\n" );
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