document.write( "Question 107254: I need all the roots and zeros to these problems
\n" ); document.write( "x^3+3x^2-5x-4=0
\n" ); document.write( "x^4-2x^3-7x^2+18x-18+=0
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Algebra.Com's Answer #78114 by Fombitz(32388)\"\" \"About 
You can put this solution on YOUR website!
First example.
\n" ); document.write( "A quick graph of the function shows that x=-4 looks like a root of the equation.
\n" ); document.write( "\"+graph%28+300%2C+300%2C+-5%2C+5%2C+-10%2C+10%2C+x%5E3%2B3x%5E2-5x-4%29+\"
\n" ); document.write( "\"f%28x%29=x%5E3%2B3x%5E2-5x-4\"
\n" ); document.write( "\"f%284%29=%28-4%29%5E3%2B3%2A%28-4%29%5E2-5%2A%28-4%29-4\"
\n" ); document.write( "\"f%284%29=-64%2B48%2B20-4\"
\n" ); document.write( "\"f%284%29=0\"
\n" ); document.write( "You can then find the polynomial g(x) such that
\n" ); document.write( "\"f%28x%29=g%28x%29%2A%28x%2B4%29\"
\n" ); document.write( "where \"g%28x%29=ax%5E2%2Bbx%2Bc\" and
\n" ); document.write( "\"f%28x%29=%28ax%5E2%2Bbx%2Bc%29%2A%28x%2B4%29\"
\n" ); document.write( "\"f%28x%29=ax%5E3%2B%28b%2B4a%29x%5E2%2B%28c%2B4b%29%2Ax%2B4c\"
\n" ); document.write( "Compare that to your original equation.
\n" ); document.write( "\"f%28x%29=x%5E3%2B3x%5E2-5x-4\" and you see that
\n" ); document.write( "1.\"a=1\"
\n" ); document.write( "2.\"b%2B4a=3\"
\n" ); document.write( "3.\"c%2B4b=-5\"
\n" ); document.write( "4.\"4c=-4\"
\n" ); document.write( "From 1 and 2,
\n" ); document.write( "\"b%2B4=3\"
\n" ); document.write( "\"b=-1\"
\n" ); document.write( "From 4,
\n" ); document.write( "\"4c=-4\"
\n" ); document.write( "\"c=-1\"
\n" ); document.write( "\"g%28x%29=x%5E2-x-1\"
\n" ); document.write( "You can then find the roots of g(x) using the quadratic equation.
\n" ); document.write( "\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"
\n" ); document.write( "\"x+=+%28-%28-1%29+%2B-+sqrt%28+%28-1%29%5E2-4%2A1%2A%28-1%29+%29%29%2F%282%2A1%29+\"
\n" ); document.write( "The roots of g(x) are then
\n" ); document.write( "\"x+=+%281+%2B-+sqrt%285%29%29%2F%282%29+\"
\n" ); document.write( "or approximately, x=-0.62 and x=1.62 \r
\n" ); document.write( "\n" ); document.write( "Second example.
\n" ); document.write( "A quick graph of the function shows that x=-3 and x=3 look like roots of the equation.
\n" ); document.write( "\"+graph%28+300%2C+300%2C+-5%2C+5%2C+-10%2C+10%2C+x%5E4-2x%5E3-7x%5E2%2B18x-18%29+\"
\n" ); document.write( "\"h%28x%29=x%5E4-2x%5E3-7x%5E2%2B18x-18\"
\n" ); document.write( "\"h%28-3%29=81%2B54-63-54-18\"
\n" ); document.write( "\"h%28-3%29=0\"
\n" ); document.write( "\"h%28x%29=x%5E4-2x%5E3-7x%5E2%2B18x-18\"
\n" ); document.write( "\"h%283%29=81-54-63%2B54-18\"
\n" ); document.write( "\"h%283%29=0\"
\n" ); document.write( "So then you can rewrite your equation to look like.
\n" ); document.write( "\"h%28x%29=g%28x%29%2A%28x%2B3%29%2A%28x-3%29\"
\n" ); document.write( "where
\n" ); document.write( "\"g%28x%29=ax%5E2%2Bbx%2Bc\"
\n" ); document.write( "Follow the first example above to find a,b,and c.
\n" ); document.write( "Post another question if you get stuck.
\n" ); document.write( "Good luck.
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