document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=852439>Question 852439</A>: <I><SPAN STYLE=\"word-break: break-all;\"> x^4 - 10x^2 + 9 = 0 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #513346 by </B><A HREF=/tutors/aboutme.mpl?userid=JulietG><B>JulietG(1812)</B></A><img src=\"/images/stars/stars-12.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=JulietG><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=JulietG><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=513346\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> x^4 - 10x^2 + 9 = 0<BR>\n" );
document.write( "To factor, we know that the first factor will be x^2<BR>\n" );
document.write( "(x^2     )(x^2   )<BR>\n" );
document.write( "The second number factors to 9 -- so it's either 9,1 or 3,3.  3 +/- 3 is 6 or 0, so that's not it.  Therefore, it's 9 and 1.<BR>\n" );
document.write( "(x^2   9)(x^2   1)<BR>\n" );
document.write( "To find the correct sign, look at the middle number.  What combination of +9, -9 and +1, -1 will equal -10 when added?<BR>\n" );
document.write( "(x^2-9)(x^2-1)<BR>\n" );
document.write( "Put them to zero to find the possible X solutions.<BR>\n" );
document.write( "x^2-9=0<BR>\n" );
document.write( "Add 9 to each side<BR>\n" );
document.write( "x^2=9<BR>\n" );
document.write( "x=3 or -3 (when you square it, either works)<BR>\n" );
document.write( "The second solution<BR>\n" );
document.write( "x^2-1=0<BR>\n" );
document.write( "Add 1 to each side<BR>\n" );
document.write( "x^2=1<BR>\n" );
document.write( "x= 1 or -1 </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );