document.write( "Question 1077969: Let A and B be the roots of an equation x2 +ax+b=0 and let C and D be the roots of x2+cx+d=0. Express (A-C) (B-C) (A-D) (B-D) in terms of the coefficients a, b,c ,d. \n" ); document.write( "
Algebra.Com's Answer #692462 by ikleyn(52835)\"\" \"About 
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\n" ); document.write( "Let A and B be the roots of an equation x2 +ax+b=0 and let C and D be the roots of x2+cx+d=0.
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document.write( "1.  (A-C)*(B-C) = \"AB+-+BC+-+AC+-+C%5E2\" = \"b+-%28B%2BA%29%2AC+%2B+C%5E2\" = \"b+%2B+aC+%2B+C%5E2\".\r\n" );
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document.write( "    (I replaced here A+B by -a and replaced AB by b based on Vieta's formulas).\r\n" );
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document.write( "2.  (A-D)*(B-D) = \"AB+-DB+-+AD+%2B+D%5E2\" = \"b+-+%28B%2BA%29%2AD+%2B+D%5E2\" = \"b+%2B+aD+%2B+D%5E2\".\r\n" );
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document.write( "    (Again, I replaced here A+B by -a and replaced AB by b based on Vieta's formulas).\r\n" );
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document.write( "3.  Now  (A-C)*(B-C)*(A-D)*(B-D) = \"%28b+%2B+aC+%2B+C%5E2%29%2A%28b+%2B+aD+%2B+D%5E2%29\" = \r\n" );
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document.write( "    =  = (regroup)\r\n" );
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document.write( "    =  = (simplify)\r\n" );
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document.write( "    =  = \r\n" );
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document.write( "      (replace D+C = -c,  \"D%5E2%2BC%5E2\" = \"%28D%2BC%29%5E2+-+2DC\" = (-c)^2 -2d,  CD = d,  D+C = -c,  (CD)^2 = d^2  based on Vieta's formulas. You will get) \r\n" );
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document.write( "    = \"b%5E2+-+abc+%2B+b%2A%28c%5E2-2d%29+%2B+a%5E2%28-d%29+%2B+aCD%2A%28-c%29+%2B+d%5E2\" = (simplify)\r\n" );
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document.write( "    = \"b%5E2+-+abc+%2B+bc%5E2+-+2bd+-+a%5E2d+%2B+ad%2A%28-c%29+%2B+d%5E2\" = (I just got the expression via coefficients a, b, c and d !) = \r\n" );
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document.write( "    = \"%28b-d%29%5E2+-+abc+%2B+bc%5E2+-+a%5E2d+-+acd\" = \"%28b-d%29%5E2+-ac%28b%2Bd%29+%2B+bc%5E2-a%5E2d\".\r\n" );
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\n" ); document.write( "\n" ); document.write( "Answer. (A-C)*(B-C)*(A-D)*(B-D) = \"%28b-d%29%5E2+-ac%28b%2Bd%29+%2B+bc%5E2-a%5E2d\".\r
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document.write( "     This assignment is for those who firmly knows Vieta's formulas.\r\n" );
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