document.write( "Question 848794: I have to solve this equation by making appropriate substitutions:\r
\n" ); document.write( "\n" ); document.write( "x^4- 9x^2 = -20 \n" ); document.write( "

Algebra.Com's Answer #511280 by fcabanski(1391) $\"\"$ $\"About$

You can put this solution on YOUR website!
$\"x%5E4-+9x%5E2+%2B20=0\"$
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\n" ); document.write( "Substitute $\"u=x%5E2\"$

\n" ); document.write( " $\"u%5E2+-9u+%2B+20+=+0\"$
\n" ); document.write( "(u-4)(u-5) = 0

\n" ); document.write( "u = 4 or 5

\n" ); document.write( " $\"x%5E2+=+4\"$ so x = + or - 2

\n" ); document.write( " $\"x%5E2+=+5\"$ so x = + or - $\"sqrt%285%29\"$ \n" ); document.write( "

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