document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1200642>Question 1200642</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A projectile is shot straight  up from a height of 6m with an initial velocity of 80m/s. Its height in meters above the ground after t seconds is given by the equation h=6+80t-5t^2. After how many seconds does the projectile reach its maximum height, and what is this height<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #834830 by </B><A HREF=/tutors/aboutme.mpl?userid=Alan3354><B>Alan3354(69443)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Alan3354><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=Alan3354><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=834830\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A projectile is shot straight  up from a height of 6m with an initial velocity of 80m/s. Its height in meters above the ground after t seconds is given by the equation h=6+80t-5t^2. After how many seconds does the projectile reach its maximum height, and what is this height<BR>\n" );
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document.write( "h(t) = 6+80t-5t^2<BR>\n" );
document.write( "The max of the parabola is at t = -b/2a<BR>\n" );
document.write( "--> t = -80/-10 = 8 seconds<BR>\n" );
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document.write( "h(8) = 6 + 80*8 - 5*64 = 326 meters<BR>\n" );
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document.write( "Or,<BR>\n" );
document.write( "h(t) = 6+80t-5t^2<BR>\n" );
document.write( "h'(t) = 80 - 10t = 0<BR>\n" );
document.write( "t = 8<BR>\n" );
document.write( "etc </SPAN>\n" );
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