document.write( "Question 300764: Factor completely. Show work
\n" ); document.write( "y^4 - 8y^2 – 9
\n" ); document.write( "i am lost \n" ); document.write( "

Algebra.Com's Answer #215798 by Fombitz(32388) $\"\"$ $\"About$

You can put this solution on YOUR website!
Make a substitution.
\n" ); document.write( "Let $\"u=y%5E2\"$ , then $\"u%5E2=y%5E4\"$
\n" ); document.write( " $\"+y%5E4-8y%5E2-9+=u%5E2-8u-9\"$
\n" ); document.write( " $\"y%5E4-8y%5E2-9=%28u%2B1%29%28u-9%29\"$
\n" ); document.write( "Now substitute back,
\n" ); document.write( " $\"y%5E4-8y%5E2-9=%28y%5E2%2B1%29%28y%5E2-9%29\"$
\n" ); document.write( "Both can be factored as a difference of two squares,
\n" ); document.write( " $\"y%5E4-8y%5E2-9=%28y%2Bi%29%28y-i%29%28y-3%29%28y%2B3%29\"$ where $\"i=sqrt%28-1%29\"$ \n" ); document.write( "

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