document.write( "Question 378944: find the root of the equation x^4-3x^2-54=0 \n" ); document.write( "

Algebra.Com's Answer #269150 by Fombitz(32388) $\"\"$ $\"About$

You can put this solution on YOUR website!
Use a substitution.
\n" ); document.write( "Let $\"u=x%5E2\"$ , then $\"u%5E2=x%5E4\"$
\n" ); document.write( " $\"u%5E2-3u-54=0\"$
\n" ); document.write( " $\"%28u-9%29%28u%2B6%29=0\"$
\n" ); document.write( "Two solutions:
\n" ); document.write( " $\"u-9=0\"$
\n" ); document.write( " $\"u=9\"$
\n" ); document.write( " $\"x%5E2=9\"$
\n" ); document.write( " $\"highlight%28x=0+%2B-+3%29\"$
\n" ); document.write( ".
\n" ); document.write( ".
\n" ); document.write( ".
\n" ); document.write( " $\"u%2B6=0\"$
\n" ); document.write( " $\"u=-6\"$
\n" ); document.write( " $\"x%5E2=-6\"$
\n" ); document.write( " $\"highlight%28x=0+%2B-+sqrt%286%29i%29\"$
\n" ); document.write( " \n" ); document.write( "

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