document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=266090>Question 266090</A>: <I><SPAN STYLE=\"word-break: break-all;\">  Please help, solve by completing square\r<BR>\n" );
document.write( "\n" );
document.write( "x^2-4x-1=0 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #195527 by </B><A HREF=/tutors/aboutme.mpl?userid=dabanfield><B>dabanfield(803)</B></A><img src=\"/images/stars/stars-11.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=dabanfield><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=195527\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> x^2-4x-1=0\r<BR>\n" );
document.write( "\n" );
document.write( "Rewrite as:\r<BR>\n" );
document.write( "\n" );
document.write( "x^2 - 4x = 1\r<BR>\n" );
document.write( "\n" );
document.write( "We need to add a constant to both sides so that the left side becomes a perfect suqare of the form (x+a)^2.\r<BR>\n" );
document.write( "\n" );
document.write( "Since the middle term is -4x we know that the constant needs to be -4/2 = -2 which when squared is (-2)^2 = 4. So we add 4 to both sides of the equation above:\r<BR>\n" );
document.write( "\n" );
document.write( "x^2 - 4x + 4 = 1 + 4<BR>\n" );
document.write( "(x-2)^ = 5\r<BR>\n" );
document.write( "\n" );
document.write( "Taking the square root of both sides above we have x-2 = sqrt(5) or x-2 = -sqrt(5) so\r<BR>\n" );
document.write( "\n" );
document.write( "x = 2+sqrt(5) or x = 2-sqrt(5) </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );