document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=727216>Question 727216</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I am really confused on this one. Here is the problem:\r<BR>\n" );
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document.write( "A child throws a ball up a hill that makes an angle of 45 degrees with the horizontal. The ball lands 100 feet up the hill. Its trajectory is a parabola with equation y= -X^2 + ax for some number a. Find a.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #445037 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=445037\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A child throws a ball up a hill that makes an angle of 45 degrees with the horizontal. The ball lands 100 feet up the hill. Its trajectory is a parabola with equation y= -X^2 + ax for some number a. Find a.<BR>\n" );
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document.write( "The hill is the line y = x<BR>\n" );
document.write( "100 ft measured on the hill --> x = 100cos(45), y = 100sin(45)<BR>\n" );
document.write( "The point of impact is (70.7,70.7)<BR>\n" );
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document.write( "y = -x^2 + ax<BR>\n" );
document.write( "70.7 = -5000 + a*70.7<BR>\n" );
document.write( "a =~ 71.72\r<BR>\n" );
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