document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1199217>Question 1199217</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Solve for x.\r<BR>\n" );
document.write( "\n" );
document.write( "x^4 - 5x^2 -12 = 0\r<BR>\n" );
document.write( "\n" );
document.write( "I can write x^4 like this: (x^2)^2.\r<BR>\n" );
document.write( "\n" );
document.write( "Let u = x^2.\r<BR>\n" );
document.write( "\n" );
document.write( "u^2 - 5u - 12 = 0\r<BR>\n" );
document.write( "\n" );
document.write( "After using the quadratic formula, I got the following:\r<BR>\n" );
document.write( "\n" );
document.write( "u = (5 + sqrt{73})/2 and (5 - sqrt{73})/2.\r<BR>\n" );
document.write( "\n" );
document.write( "I back-substituted for u.\r<BR>\n" );
document.write( "\n" );
document.write( "x^2 = (5 + sqrt{73})/2 and x^2 = (5 - sqrt{73})/2.\r<BR>\n" );
document.write( "\n" );
document.write( "Taking the square root on both sides, I got:\r<BR>\n" );
document.write( "\n" );
document.write( "x = [(5 + sqrt{73}/2)]^(1/2)\r<BR>\n" );
document.write( "\n" );
document.write( "x = [(5 - sqrt{73}/2)]^(1/2)\r<BR>\n" );
document.write( "\n" );
document.write( "The textbook Answer for x are -2, -1, 1, 2.\r<BR>\n" );
document.write( "\n" );
document.write( "Why is my answer wrong? \r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #832975 by </B><A HREF=/tutors/aboutme.mpl?userid=ikleyn><B>ikleyn(52786)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ikleyn><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=ikleyn><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=832975\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> .\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "The textbook answers are wrong.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "You can easily check them by substituting into your original equation.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "Your answers are correct.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );