document.write( "Question 914191: Find all real solutions: x^4-16x^2-80=0 \n" ); document.write( "

Algebra.Com's Answer #554992 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Let $\"+z+=+x%5E2+\"$
\n" ); document.write( " $\"+z%5E2+-+16z+-+80+=+0+\"$
\n" ); document.write( "complete the square:
\n" ); document.write( " $\"+z%5E2+-+16z+%2B+%2816%2F2%29%5E2+=+80+%2B+%2816%2F2%29%5E2+\"$
\n" ); document.write( " $\"+z%5E2+-+16z+%2B+64+=+80+%2B+64+\"$
\n" ); document.write( " $\"+%28+z+-+8+%29%5E2+=+12%5E2+\"$
\n" ); document.write( " $\"+z+-+8+=+12+\"$
\n" ); document.write( " $\"+z+=+20+\"$
\n" ); document.write( "and also:
\n" ); document.write( " $\"+z+-+8+=+-12+\"$
\n" ); document.write( " $\"+z+=+-4+\"$
\n" ); document.write( "---------------
\n" ); document.write( " $\"+z+=+x%5E2+\"$
\n" ); document.write( " $\"+20+=+x%5E2+\"$
\n" ); document.write( " $\"+x+=+2%2Asqrt%285%29+\"$
\n" ); document.write( " $\"+x+=+-2%2Asqrt%285%29+\"$
\n" ); document.write( "and
\n" ); document.write( " $\"+z+=+x%5E2+\"$
\n" ); document.write( " $\"+-4+=+x%5E2+\"$
\n" ); document.write( " $\"+x+=+2i+\"$
\n" ); document.write( " $\"+x+=+-2i+\"$
\n" ); document.write( "these are the 4 solutions
\n" ); document.write( "You can plug them back in to check
\n" ); document.write( "The real solutions are the first 2\r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

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