document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=189928>Question 189928</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/9780618726523/algebrahomeworkh>McDougal Littell Math</A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> A baseball player hits a baseball into the air from a height of 3 feet with an initial vertical velocity of 72 feet per second. After how many seconds is the baseball 84 feet above the ground?<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 #142613 by </B><A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><B>ankor@dixie-net.com(22740)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><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=ankor@dixie-net.com><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=142613\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A baseball player hits a baseball into the air from a height of 3 feet with<BR>\n" );
document.write( " an initial vertical velocity of 72 feet per second. After how many seconds<BR>\n" );
document.write( " is the baseball 84 feet above the ground?<BR>\n" );
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document.write( "The equation for this is:<BR>\n" );
document.write( "h = -16t^2 + 72t + 3<BR>\n" );
document.write( "Where:<BR>\n" );
document.write( "h = height at t seconds<BR>\n" );
document.write( "-16t^2 is the downward pull of gravity<BR>\n" );
document.write( "72t is the vertical velocity upward<BR>\n" );
document.write( "3 is the initial height at t=0<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Find t when height is 84 ft<BR>\n" );
document.write( "-16t^2 + 72t + 3 = 84<BR>\n" );
document.write( "Arrange as a quadratic equation:<BR>\n" );
document.write( "-16t^2 + 72t + 3 - 84 = 0<BR>\n" );
document.write( "-16t^2 + 72t - 81 = 0<BR>\n" );
document.write( "multiply equation by -1 to change the signs, easier to factor<BR>\n" );
document.write( "16t^2 - 72t + 81 = 0<BR>\n" );
document.write( "this is a perfect square<BR>\n" );
document.write( "(4t - 9)(4t - 9) = 0<BR>\n" );
document.write( "4t = +9<BR>\n" );
document.write( "t = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=9%2F4 ALIGN=MIDDLE  ALT=\"9%2F4\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "t = 2.25 sec it will be at 84' (this is also the highest point (vertex)) </SPAN>\n" );
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