document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=604590>Question 604590</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I need help finding the vertex of the parabola: y= -6.25x²+ 150x + 7200?\r<BR>\n" );
document.write( "\n" );
document.write( "I have graphed it and found the vertex to be (12, 8100) but I need to be able to find it algebraically. I tried taking the derivative but I'm not sure I was doing that right or if thats how I should approach it. Please explain your steps, so that i can learn what and why you are doing what you do. Thanks in advance for all the help. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #381284 by </B><A HREF=/tutors/aboutme.mpl?userid=nerdybill><B>nerdybill(7384)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=nerdybill><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=nerdybill><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=381284\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> y= -6.25x²+ 150x + 7200<BR>\n" );
document.write( ".<BR>\n" );
document.write( "The x-value of the vertex is at:<BR>\n" );
document.write( "x = -b/(2a)  (from the \"quadratic formula\" w/o the radical)<BR>\n" );
document.write( "x = -150/(2(-6.25)<BR>\n" );
document.write( "x = -150/(-12.5)<BR>\n" );
document.write( "x = 150/12.5<BR>\n" );
document.write( "x = 12<BR>\n" );
document.write( ".<BR>\n" );
document.write( "To find the y-value, plug the above back into the equation:<BR>\n" );
document.write( "y= -6.25x²+ 150x + 7200<BR>\n" );
document.write( "y= -6.25(12)²+ 150(12) + 7200<BR>\n" );
document.write( "y= 8100\r<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );