document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=668717>Question 668717</A>: <I><SPAN STYLE=\"word-break: break-all;\"> How do I solve this?\r<BR>\n" );
document.write( "\n" );
document.write( "A projectile is thrown upward so that its distance above the ground after t seconds is  <BR>\n" );
document.write( "h=-13t^2+520t. After how many seconds does it reach its maximum height?<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #415805 by </B><A HREF=/tutors/aboutme.mpl?userid=jenabee><B>jenabee(1)</B></A><img src=\"/images/stars/iconNewId_16x16.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jenabee><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=415805\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> h=-13t^2+520t since a= -13, the parabola will open down. \r<BR>\n" );
document.write( "\n" );
document.write( "Use -b/2a to find the x-value. This value will represent the number of seconds the projectile will meet its maximum height.\r<BR>\n" );
document.write( "\n" );
document.write( "a= -13<BR>\n" );
document.write( "b=250\r<BR>\n" );
document.write( "\n" );
document.write( "-250/2(-13)= 20<BR>\n" );
document.write( "Therefore, in 20 seconds, the projectile will meet its maximum height. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );