document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=314607>Question 314607</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Jack throws a ball straight up in the air.  The equation, h(t)= -16tsquared+64t+5 gives the height (in feet) of the ball from the ground t seconds after it is thrown.  How long does it take for the ball to hit the ground?\r<BR>\n" );
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document.write( "I have already figured out the maximum height, I think, as 75 feet.  Which takes 5 seconds.\r<BR>\n" );
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document.write( "Thanks. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #224971 by </B><A HREF=/tutors/aboutme.mpl?userid=texttutoring><B>texttutoring(324)</B></A><img src=\"/images/stars/stars-10.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=texttutoring><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=texttutoring><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=224971\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> I think that the max height is 69 feet, and it occurs at 2 seconds.\r<BR>\n" );
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document.write( "Make sure you complete the square:\r<BR>\n" );
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document.write( "h(t) = -16t^2+64t+5<BR>\n" );
document.write( "= -16(t^2 - 4t) + 5<BR>\n" );
document.write( "=-16(t^2 -4t + 4) + 5 + 64<BR>\n" );
document.write( "=-16(t-2)^2 + 69\r<BR>\n" );
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document.write( "This a parabola with vertex at (2,69). \r<BR>\n" );
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document.write( "If you want to find the time that it takes to hit the ground, set h=0 and use the quadratic formula to solve for t.\r<BR>\n" );
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document.write( "0=-16t^2+64t+5\r<BR>\n" );
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document.write( "The quadratic formula should give you two answers: t=-0.77 and t=4.077\r<BR>\n" );
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document.write( "You have to choose the positive answer, as time cannot be negative.\r<BR>\n" );
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document.write( "Therefore, the ball hits the ground at 4.077 seconds. </SPAN>\n" );
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