document.write( "Question 575503: please help me solve this equation
\n" ); document.write( "3x^4-11x^2-20=0 \n" ); document.write( "

Algebra.Com's Answer #369500 by Earlsdon(6294) $\"\"$ $\"About$

You can put this solution on YOUR website!
Sometimes it simpifies things a bit by temporarily using a substitute variable:
\n" ); document.write( "Temporarily let $\"x%5E2+=+y\"$ so now you have:
\n" ); document.write( " $\"3y%5E2-11y-20+=+0\"$ Factor:
\n" ); document.write( " $\"%283y%2B4%29%28y-5%29+=+0\"$ Solve for y:
\n" ); document.write( " $\"3y%2B4+=+0\"$ or $\"y-5+=+0\"$ so...
\n" ); document.write( " $\"y+=+-4%2F3\"$ or $\"y+=+5\"$ Replace $\"y+=+x%5E2\"$ to get...
\n" ); document.write( " $\"x%5E2+=+-4%2F3\"$ or $\"x%5E2+=+5\"$ Taking the square roots, we get...
\n" ); document.write( " $\"x+=+sqrt%28-4%2F3%29\"$ or $\"x+=+-sqrt%28-4%2F3%29\"$ or $\"x+=+sqrt%285%29\"$ or $\"x+=+-sqrt%285%29\"$
\n" ); document.write( "If you need your answers in approximate form, then...
\n" ); document.write( " $\"x+=+2.236\"$ or $\"x+=+-2.236\"$ or $\"x+=+1.155i\"$ or $\"x+=+-1.155i\"$
\n" ); document.write( "Here's what the graph looks like:
\n" ); document.write( " $\"graph%28400%2C400%2C-5%2C5%2C-30%2C5%2C3x%5E4-11x%5E2-20%29\"$ \n" ); document.write( "

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