document.write( "Question 20379: How do you factor x^4 - 3x^2 - 4 \n" ); document.write( "

Algebra.Com's Answer #9822 by longjonsilver(2297) $\"\"$ $\"About$

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a little mental leap is required here.\r
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\n" ); document.write( "\n" ); document.write( "Let $\"y=x%5E2\"$ , so that $\"y%5E2+=+x%5E4\"$ . Are these definitions OK?\r
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\n" ); document.write( "\n" ); document.write( "Right, $\"x%5E4+-+3x%5E2+-+4\"$ then becomes $\"y%5E2+-+3y+-+4\"$ which is a normal quadratic that factorises easily to (y-4)(y+1). \r
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\n" ); document.write( "\n" ); document.write( "Hence, we have $\"%28x%5E2+-+4%29%28x%5E2+%2B+1%29\"$ \r
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\n" ); document.write( "\n" ); document.write( "jon.
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