document.write( "Question 150618: Please show me how to work out this problem. I know the roots are -1/3, -1/2, and 3, but I don't know how to work the problem by hand to find the answer. Please help so I know how to solve this kind of problem in the future!\r
\n" ); document.write( "\n" ); document.write( "-21x^3 + 53x^2 + 53x + 20 = 3x^3 + x^2 -3x + 8
\n" ); document.write( "-24x^3 + 52x^2 + 56x + 12 = 0
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Algebra.Com's Answer #110551 by Edwin McCravy(20055)\"\" \"About 
You can put this solution on YOUR website!
Please show me how to work out this problem. I know the roots are -1/3, -1/2, and 3, but I don't know how to work the problem by hand to find the answer. Please help so I know how to solve this kind of problem in the future! \r
\n" ); document.write( "\n" ); document.write( "\"-21x%5E3+%2B+53x%5E2+%2B+53x+%2B+20+=+3x%5E3+%2B+x%5E2+-3x+%2B+8\"
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document.write( "That's correct.  Now observe that all the coefficients\r\n" );
document.write( "can be divided by -4, so we do that:\r\n" );
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document.write( "\"6x%5E3+-+13x%5E2+-+14x+-+3+=+0\"\r\n" );
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document.write( "If there is any rational root, its numerator must divide\r\n" );
document.write( "evenly into the absolute value of the constant term, and \r\n" );
document.write( "its denominator must divide evenly into the absolute value\r\n" );
document.write( "of the coefficient of the leading term (the term with the\r\n" );
document.write( "largest exponent.\r\n" );
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document.write( "So the possible numerators are 1 and 3, for these are the \r\n" );
document.write( "only integers which will divide evenly into 3.\r\n" );
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document.write( "the possible denominators are 1, 2, 3 and 6, for these are the \r\n" );
document.write( "only integers which will divide evenly into 6.  \r\n" );
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document.write( "So all possible rational (common fraction) roots are\r\n" );
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document.write( "±\"1%2F1\", ±\"1%2F2\", ±\"1%2F3\", ±\"1%2F6\", ±\"3%2F1\", ±\"3%2F2\", ±\"3%2F3\", ±\"3%2F6\".\r\n" );
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document.write( "Which reduce to:\r\n" );
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document.write( "±\"1\", ±\"1%2F2\", ±\"1%2F3\", ±\"1%2F6\", ±\"3\", ±\"3%2F2\", ±\"1\", ±\"1%2F2\".\r\n" );
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document.write( "Eliminating the duplicates, all possible rational roots are:\r\n" );
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document.write( "±\"1\", ±\"1%2F2\", ±\"1%2F3\", ±\"1%2F6\", ±\"3\", ±\"3%2F2\".\r\n" );
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document.write( "First we try the easiest possible root 1, using synthetic division:\r\n" );
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document.write( "    1| 6 -13  -14  -3 \r\n" );
document.write( "     |     6   -7 -21 \r\n" );
document.write( "       6  -7  -21 -24\r\n" );
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document.write( "That doesn't leave a 0 remainder so 1 is not a root.\r\n" );
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document.write( "So we try the next easiest possible root -1, using synthetic division:\r\n" );
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document.write( "   -1| 6 -13 -14 -3 \r\n" );
document.write( "     |    -6  19 -5 \r\n" );
document.write( "       6 -19   5 -8\r\n" );
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document.write( "That doesn't leave a 0 remainder either so -1 is not a root.\r\n" );
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document.write( "So we try the next easiest possible root 3, using synthetic division:\r\n" );
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document.write( "    3| 6  -13  -14 -3 \r\n" );
document.write( "     |     18   15  3 \r\n" );
document.write( "       6    5    1  0\r\n" );
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document.write( "That leaves a 0 remainder so 3 is a root.  So we have now\r\n" );
document.write( "factored the left side of:\r\n" );
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document.write( "\"6x%5E3+-+13x%5E2+-+14x+-+3+=+0\"\r\n" );
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document.write( "as\r\n" );
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document.write( "\"%28x-3%29%286x%5E2%2B5x%2B1%29=0\"\r\n" );
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document.write( "Now we factor the second parentheses:\r\n" );
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document.write( "\"%28x-3%29%282x%2B1%29%283x%2B1%29=0\"\r\n" );
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document.write( "Now we use the zero factor property\r\n" );
document.write( "to set each factor = 0\r\n" );
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document.write( "\"x-3=0\" gives the solution \"x=3\"\r\n" );
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document.write( "\"2x%2B1=0\" gives the solution \"x=-1%2F2\"\r\n" );
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document.write( "\"3x%2B1=0\" gives the solution \"x=-1%2F3\"\r\n" );
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document.write( "Edwin

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