document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=193559>Question 193559</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/9780395977255/algebrahomeworkh>algebra and trigonometry structure and method book 2</A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> ``Find the vertex, focus, directrix, and axis of symmetry of each parabola. <BR>\n" );
document.write( "x^2+8y+4x-4=0<BR>\n" );
document.write( "We have been using the formulas y-k=a(x-h)^2 and x-h=a(y-k)^2 I don't understand <BR>\n" );
document.write( "which to use here, even after completing the square and its confusing because I <BR>\n" );
document.write( "don't know which is which. please explain and be specific. thank you. We also <BR>\n" );
document.write( "use the fact that the focus is F(h,k+c) when a=1/4c. Please explain in these <BR>\n" );
document.write( "terms so that I can understand. thank you </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #145288 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=145288\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Find the vertex, focus, directrix, and axis of symmetry of each parabola. <BR>\n" );
document.write( "x^2+8y+4x-4=0<BR>\n" );
document.write( "We have been using the formulas y-k=a(x-h)^2 and x-h=a(y-k)^2 I don't understand which to use here, even after completing the square and its confusing because I don't know which is which. please explain and be specific. thank you. We also use the fact that the focus is F(h,k+c) when a=1/4c. Please explain in these terms so that I can understand. thank you<BR>\n" );
document.write( "-------------<BR>\n" );
document.write( "x^2+8y+4x-4=0<BR>\n" );
document.write( "-----------------<BR>\n" );
document.write( "Complete the square on the x-terms<BR>\n" );
document.write( "x^2 + 4x + ? = -8y+4 + ?<BR>\n" );
document.write( "x^2 + 4x + 4 = -8y + 4+4<BR>\n" );
document.write( "(x+2)^2 = -8(y-1)<BR>\n" );
document.write( "------------------------<BR>\n" );
document.write( "Rearrange:<BR>\n" );
document.write( "(x-1) = (-1/8)(y+2)^2<BR>\n" );
document.write( "h = 1, k= -2, a = -1/8 = (1/4)c <BR>\n" );
document.write( "c = -1/2<BR>\n" );
document.write( "----------------------<BR>\n" );
document.write( "Find the vertex, focus, directrix, and axis of symmetry of each parabola.<BR>\n" );
document.write( "Vertex = (h,k) = (1,-2)<BR>\n" );
document.write( "Focus = (h+c, k) because this parabola is opening to the left.<BR>\n" );
document.write( "Focus = (1-(1/2),-2) = ((1/2),-2)<BR>\n" );
document.write( "Directrix: x = h - c = 1+1/2 = 3/2<BR>\n" );
document.write( "Axis of symmetry: Horizontal line passing thru the vertex:<BR>\n" );
document.write( "y = -2<BR>\n" );
document.write( "=================================================================<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );