document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=225644>Question 225644</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The height in feet for a ball thrown upward at 48 feet per second is given by <BR>\n" );
document.write( "s(t)= -16t^2 + 48feet, where t is the time in seconds after the ball is tossed. What is the maximum height that the ball will reach? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #168291 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=168291\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> s(t)= -16t^2 + 48t<BR>\n" );
document.write( "Find the 2 times that s = 0.  It takes the same time to go up as to fall back down, so at the mid-time it's at max height.<BR>\n" );
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document.write( "-16t^2 + 48t = 0<BR>\n" );
document.write( "t = 0 (at the start)<BR>\n" );
document.write( "t = 3 (return to Earth)<BR>\n" );
document.write( "t at max height = 1.5 seconds<BR>\n" );
document.write( "s(1.5) = -16*2.25 + 48*1.5<BR>\n" );
document.write( "= -36 + 72<BR>\n" );
document.write( "= 36 ft<BR>\n" );
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document.write( "Or, find the vertex of the parabola<BR>\n" );
document.write( "It's at t = -b/2a = -48/-32 = 1.5<BR>\n" );
document.write( "Same answer. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );