document.write( "Question 1183896: FInd the quadratic equation each of whose roots is the sum of a root and its reciprocal of the quadratic equation 2x^2 + 3x + 4 = 0. \n" ); document.write( "
Algebra.Com's Answer #814385 by ikleyn(52781)\"\" \"About 
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\n" ); document.write( "FInd the quadratic equation each of whose roots is the sum of a root
\n" ); document.write( "and its reciprocal of the quadratic equation 2x^2 + 3x + 4 = 0.
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\n" ); document.write( "\n" ); document.write( "            You are talking about another interpretation of the problem, previously solved.\r
\n" ); document.write( "\n" ); document.write( "            This interpretation is slightly different problem, but still very close to the previous one.\r
\n" ); document.write( "\n" ); document.write( "            It can be solved using the same method and metodology.\r
\n" ); document.write( "\n" ); document.write( "            Again, this problem is to apply the  Vieta's theorem several times.\r
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document.write( "Let  \" a \"  and  \" b \"  be the roots of the given equation.\r\n" );
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document.write( "Then according to Vieta's theorem, the sum  (a+b)  is equal to  \"-3%2F2\" :  a + b = \"-3%2F2\".\r\n" );
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document.write( "According to the same theorem, the product of the routs  ab  is equal to  \"4%2F2\" = 2.\r\n" );
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document.write( "OK.  \r\n" );
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document.write( "HENCE, the projected equation has the value  A = \"a%2B1%2Fa\"  as one of its roots, and has the value B = \"b%2B1%2Fb\"  as the another root.\r\n" );
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document.write( "The sum of the roots A + B is  A + B = \"a%2B1%2Fa%2Bb%2B1%2Fb\" = \"%28a%2Bb%29+%2B+%281%2Fa%2B1%2Fb%29\" = \"%28a%2Bb%29+%2B+%28a%2Bb%29%2F%28ab%29\".\r\n" );
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document.write( "We substitute here  a+b = \"-3%2F2\"  and  ab = 2,  and we get  A + B = \"%28-3%2F2%29\" + \"%28%28-3%2F2%29%29%2F2\" = \"-3%2F2+-+3%2F4\" = \"-9%2F4\".\r\n" );
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document.write( "Next, A*B = \"%28a%2B1%2Fa%29%2A%28b%2B1%2Fb%29\" = \"ab+%2B+%28b%2Fa%2Ba%2Fb%29+%2B+1%2F%28ab%29\" = 2 + \"%28a%5E2+%2B+b%5E2%29%2F%28ab%29\" + \"1%2F2\" = 2 \"1%2F2\" + \"%28%28a%5E2+%2B+b%5E2+%2B+2ab%29-2ab%29%2F%28ab%29\" = 2 \"1%2F2\" + \"%28%28a%2Bb%29%5E2-2ab%29%2Fab\" = \r\n" );
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document.write( "          = 2 \"1%2F2\" + \"%28%28-3%2F2%29%5E2-+2%2A2%29%2F2\" = 2 \"1%2F2\" + \"%289%2F4-4%29%2F2\" = 2 \"1%2F2\" + \"%28%28-7%2F4%29%29%2F2\" = 2 \"1%2F2\" - \"7%2F8\" = \"20%2F8\" - \"7%2F8\" = \"13%2F8\".\r\n" );
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document.write( "HENCE, applying the Vieta's theorem again, the projected equation has the form\r\n" );
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document.write( "    x^2 - (A+B)x + AB = 0,   or   \"x%5E2+%2B+%289%2F4%29x+%2B+13%2F8\" = 0.\r\n" );
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document.write( "You can have this equation with integer coefficient by multiplying its terms by 8.  You will get then the final equation as\r\n" );
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document.write( "    \"8x%5E2+%2B+18x+%2B+13\" = 0.\r\n" );
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\n" ); document.write( "\n" ); document.write( "As I said,  the same methodology works.\r
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\n" ); document.write( "\n" ); document.write( "I think,  that after my previous solution,  an advanced student would be able to solve this one  ON  HIS  OWN.\r
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\n" ); document.write( "\n" ); document.write( "In any case,  I am glad to hear your response,  which was meaningful,  what  RARELY  HAPPENS  at this forum.\r
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