document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=171383>Question 171383</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A paper airplane follows a parabolic path with h=-1/4t^2+t+3, where h is height in meters, and t is time in seconds. Algebraically determine how long it takes for the paper airplane to hit 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 #126675 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=126675\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> h=-1/4t^2+t+3<BR>\n" );
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document.write( "When the ball hits the ground, the height is zero.<BR>\n" );
document.write( "So, set h to 0 and solve for t:<BR>\n" );
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document.write( "h=-1/4t^2+t+3<BR>\n" );
document.write( "0 = -1/4t^2+t+3<BR>\n" );
document.write( "multiply both sides by -4:<BR>\n" );
document.write( "0 = t^2-4t-12<BR>\n" );
document.write( "factoring:<BR>\n" );
document.write( "0 = (t-6)(t+2)<BR>\n" );
document.write( "t = {-2, 6}<BR>\n" );
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document.write( "Tossing out the negative solution:<BR>\n" );
document.write( "t = 6 seconds<BR>\n" );
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