document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=81488>Question 81488</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/0078656095/algebrahomeworkh>Algebra 2</A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> I can not figure out how to write an equation for parabola  <BR>\n" );
document.write( "   focus (3,8),directrix y=4 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #58336 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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=58336\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> write an equation for parabola  <BR>\n" );
document.write( "   focus (3,8),directrix y=4<BR>\n" );
document.write( "----------<BR>\n" );
document.write( "Draw the line y=4.<BR>\n" );
document.write( "Plot the point (3,8)<BR>\n" );
document.write( "The focus is above the directrix and is 2p away from it.<BR>\n" );
document.write( "So 2p=4; p=2<BR>\n" );
document.write( "The vertex is half way between the focus and the directrix.<BR>\n" );
document.write( "So the vertex is (3,6)<BR>\n" );
document.write( "-----------<BR>\n" );
document.write( "EQUATION:<BR>\n" );
document.write( "4p(y-k)=(x-h)^2<BR>\n" );
document.write( "8(y-6)=(x-3)^2<BR>\n" );
document.write( "8y-48=x^2-6x+9<BR>\n" );
document.write( "8y=x^2-6x+57<BR>\n" );
document.write( "y=(1/8)x^2-(3/4)x+57/8<BR>\n" );
document.write( "===========<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );