document.write( "Question 854182: i do not understand how x^4-9x^2 equals 20 \n" ); document.write( "

Algebra.Com's Answer #514506 by josgarithmetic(39617) $\"\"$ $\"About$

You can put this solution on YOUR website!
$\"x%5E4-9x%5E2=20\"$ \r
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\n" ); document.write( "\n" ); document.write( "The equation is in quadratic form.
\n" ); document.write( " $\"x%5E4-9x%5E2-20=0\"$ which seems not factorable.\r
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\n" ); document.write( "\n" ); document.write( "Let v=x^2 and first solve for v.
\n" ); document.write( " $\"v%5E2-9v-20=0\"$
\n" ); document.write( "Discriminant is $\"9%2A9-4%28-20%29=81%2B80=161\"$ and $\"161=7%2A23\"$ .
\n" ); document.write( " $\"v=%289%2B-+sqrt%28161%29%29%2F2\"$
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\n" ); document.write( "Remember how v was assigned and substituted.
\n" ); document.write( " $\"highlight%28x=0%2B-+sqrt%28%289%2B-+sqrt%28161%29%29%2F2%29%29\"$ , which is itself four different expressions, four different values.\r
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\n" ); document.write( "\n" ); document.write( "* The zero is included only to allow for rendering; it can otherwise be omitted. \n" ); document.write( "

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