document.write( "Question 1099591: if alpha,beta,gamma,and delta(symbols) are the roots of x^4-2x^3+4x^2+6x-21=0 if alpha + beta =0, solve the equation completely. \n" ); document.write( "
Algebra.Com's Answer #714050 by ikleyn(52781)\"\" \"About 
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\n" ); document.write( "if alpha,beta,gamma,and delta(symbols) are the roots of x^4-2x^3+4x^2+6x-21=0 if alpha + beta =0, solve the equation completely.
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document.write( "I will use  \"p\"  and  \"q\"  instead of \"alpha\" and \"beta\" to make my writing easier.\r\n" );
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document.write( "So, I am given that p and q are the roots of the equation \r\n" );
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document.write( "\"x%5E4+-+2x%5E3+%2B+4x%5E2+%2B+6x+-+21\" = 0,\r\n" );
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document.write( "such that  p = -q.  Then the fact that p and q are the roots means\r\n" );
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document.write( "\"p%5E4+-+2%2Ap%5E3+%2B+4%2Ap%5E2+%2B+6%2Ap+-+21\" = 0,                (1)     and\r\n" );
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document.write( "\"%28-p%29%5E4+-+2%2A%28-p%29%5E3+%2B+4%2A%28-p%29%5E2+%2B+6%2A%28-p%29+-+21\" = 0,       (2),    or\r\n" );
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document.write( "\"p%5E4+%2B+2%2Ap%5E3+%2B+4%2Ap%5E2+-+6p+-+21\" = 0.                 (3)\r\n" );
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document.write( "Now subtract eq(1) from eq(3) (both sides). You will get\r\n" );
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document.write( "\"4p%5E3+-+12p\" = 0,    or  \r\n" );
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document.write( "\"4p%2A%28p%5E2-3%29\" = 0.\r\n" );
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document.write( "It implies that  p = +/- \"sqrt%283%29\".\r\n" );
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document.write( "Thus two roots of the given polynomial are  \"sqrt%283%29\"  and  \"-sqrt%283%29\".\r\n" );
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document.write( "Then the polynomial is divisible by  \"%28x-sqrt%283%29%29%2A%28x%2Bsqrt%283%29%29\" = \"x%5E2-3\".\r\n" );
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document.write( "The quotient is  \"x%5E2+-2x+%2B+7\".\r\n" );
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document.write( "The roots of the last quadratic polynomial are  \"1+%2B+i%2Asqrt%286%29\"  and  \"1+-+i%2Asqrt%286%29\".\r\n" );
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document.write( "Thus the roots of the original polynomial are  \"sqrt%283%29\",  \"-sqrt%283%29\",  \"1+%2B+i%2Asqrt%286%29\"  and  \"1+-+i%2Asqrt%286%29\".\r\n" );
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