document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=66792>Question 66792</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Solve by completing the square.<BR>\n" );
document.write( "2x^2-12x-18=0<BR>\n" );
document.write( "How do you do it. Thanks </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #47493 by </B><A HREF=/tutors/aboutme.mpl?userid=ptaylor><B>ptaylor(2198)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ptaylor><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=ptaylor><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=47493\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Solve by completing the square.<BR>\n" );
document.write( "2x^2-12x-18=0<BR>\n" );
document.write( "How do you do it. Thanks\r<BR>\n" );
document.write( "\n" );
document.write( "2x^2-12x-18=0  This is in standard form with A=2, B=-12 and C=-18.  \r<BR>\n" );
document.write( "\n" );
document.write( "First, divide each term by 2;  (we want A to equal 1) and we get:\r<BR>\n" );
document.write( "\n" );
document.write( "x^2-6x-9=0  now add 9 to both sides (we are setting up the left side so we can complete the square) and we have:\r<BR>\n" );
document.write( "\n" );
document.write( "x^2-6x+9-9=9<BR>\n" );
document.write( "x^2-6x=9  Now we will complete the square on the left side.  In other words, we will select a C for the left side that results in the left side being a perfect square.  When A=1, we can take half B , square it, and add it to both sides.  We will now have a perfect square on the left side.  Another way to look at it is: when A=1, then B is the sum of the factors of C.  Here, we are choosing the factors of C that results in a perfect square and this will work in most every case.\r<BR>\n" );
document.write( "\n" );
document.write( "(1/2)B=-3  squaring it, we get 9.  So we add 9 to both sides\r<BR>\n" );
document.write( "\n" );
document.write( "x^2-6x+9=18<BR>\n" );
document.write( "(x-3)^2=18   take the square root of both sides<BR>\n" );
document.write( "x-3=+or-sqrt(18)=+or-sqrt(9)(2)<BR>\n" );
document.write( "x=3+3sqrt(2)=3(1+sqrt(2))<BR>\n" );
document.write( "x=3-3sqrt(2)=3(1-sqrt(2))\r<BR>\n" );
document.write( "\n" );
document.write( "Ck by using the quadratic formula\r<BR>\n" );
document.write( "\n" );
document.write( "Hope this helps---ptaylor\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );