document.write( "Question 731291: one zero of f(x)=x^4-3x^3-12x-16 is -2i. what are the other zeros of the function?\r
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Algebra.Com's Answer #447080 by josgarithmetic(39620)\"\" \"About 
You can put this solution on YOUR website!
TWO of the roots are -2i and +2i. The -2i was given. The +2i is a root because complex roots to polynomial equations occur in conjugate pairs.\r
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\n" ); document.write( "\n" ); document.write( "Using those two roots, find the corresponding quadratic factors of f(x), and use polynomial division to find the other quadratic factor.\r
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\n" ); document.write( "\n" ); document.write( "\"%28x%2B2i%29%28x-2i%29=x%5E2-%282i%29%5E2\"=x^2-(-1)*4=\"highlight%28x%5E2%2B4%29\"
\n" ); document.write( "You want to divide \"x%5E4-3x%5E3-12x-16\" by \"x%5E2%2B4\". You should use the divisor in the form, \"x%5E2%2B0%2Ax%2B4\".\r
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\n" ); document.write( "\n" ); document.write( "The polynomial division, \"%28x%5E4-3x%5E3%2B0%2Ax%5E2-12x-16%29%2F%28x%5E2%2B0%2Ax%2B4%29=x%5E2-3x-4\"
\n" ); document.write( "and that quadratic polynomial is factorable into \"%28x%2B1%29%28x-4%29\".\r
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\n" ); document.write( "\n" ); document.write( "So the function is factorable into \"highlight%28f%28x%29=%28x%5E2%2B4%29%28x%2B1%29%28x-4%29%29\". The roots found which were not given in the description but were asked for are -1 and +4.
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