document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=249121>Question 249121</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Find all exact zeros (both real and complex) of the function:<BR>\n" );
document.write( " f x = 4x^4 - 21x^2 - 25. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #181503 by </B><A HREF=/tutors/aboutme.mpl?userid=edjones><B>edjones(8007)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=edjones><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=edjones><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=181503\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> 4x^4 - 21x^2 - 25=0<BR>\n" );
document.write( "4*-25=-100<BR>\n" );
document.write( "4 & -25 are factors of -100 whose sum is -21<BR>\n" );
document.write( "4x^4+4x^2-25x^2-25=0<BR>\n" );
document.write( "4x^2(x^2+1)-25(x^2+1)=0 factor by grouping<BR>\n" );
document.write( "(4x^2-25)(x^2+1)=0<BR>\n" );
document.write( "(2x+5)(2x-5)(x^2+1)=0<BR>\n" );
document.write( "2x=-5, x=-5/2<BR>\n" );
document.write( "2x=5, x=5/2<BR>\n" );
document.write( "x^2=-1, x=sqrt(-1), x=i<BR>\n" );
document.write( "x=-sqrt(-1), x=-i<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Ed </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );