document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=675395>Question 675395</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A football initially on the ground is kicked in the air and follows a parabolic path after 2 seconds the football is 6 meters off the ground it reaches a maximum height of 8 meters after 4 seconds . Find the height of the football 7 seconds after the ball is kicked? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #419846 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=419846\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A football initially on the ground is kicked in the air and follows a parabolic<BR>\n" );
document.write( " path after 2 seconds the football is 6 meters off the ground it reaches a<BR>\n" );
document.write( " maximum height of 8 meters after 4 seconds.<BR>\n" );
document.write( " Find the height of the football 7 seconds after the ball is kicked?<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Using the form y = ax^2 + bx + c, where, y is the height in meters,<BR>\n" );
document.write( " x = time in seconds, the ball starts at ground level therefore c = 0<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Two ordered pairs to find a, and b<BR>\n" );
document.write( "x=2; y=6<BR>\n" );
document.write( "4a + 2b = 6<BR>\n" );
document.write( "and<BR>\n" );
document.write( "x=4, y=8<BR>\n" );
document.write( "16a + 4b = 8<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Use elimination, multiply the 1st equation by 2, subtract from the 2nd equation<BR>\n" );
document.write( "16a + 4b = 8<BR>\n" );
document.write( "8a  + 4b = 12<BR>\n" );
document.write( "----------------subtraction eliminates b, find a<BR>\n" );
document.write( "8a = -4<BR>\n" );
document.write( "a = -4/8<BR>\n" );
document.write( "a = -.5<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Find b using the 1st original equation<BR>\n" );
document.write( "4(-.5) + 2b = 6<BR>\n" );
document.write( "-2 + 2b = 6<BR>\n" );
document.write( "2b = 6 + 2<BR>\n" );
document.write( "b = 8/2<BR>\n" );
document.write( "b = 4<BR>\n" );
document.write( ":<BR>\n" );
document.write( "The equation: y = -.5x^2 + 4x<BR>\n" );
document.write( "Find the height when x = 7<BR>\n" );
document.write( "y = -.5(7^2) + 4(7)<BR>\n" );
document.write( "y = -24.5 + 28<BR>\n" );
document.write( "y = 3.5 meters after 7 seconds<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Graphically<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+graph%28+300%2C+200%2C+-4%2C+10%2C+-4%2C+12%2C+-.5x%5E2%2B4x%29+ ALIGN=MIDDLE  ALT=\"+graph%28+300%2C+200%2C+-4%2C+10%2C+-4%2C+12%2C+-.5x%5E2%2B4x%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );