document.write( "Question 1051725: find the range of values of k for which kx+y=3 meets x²+y²=5 in two distinct points \n" ); document.write( "
Algebra.Com's Answer #667227 by ikleyn(52778)\"\" \"About 
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\n" ); document.write( "find the range of values of k for which kx+y=3 meets x²+y²=5 in two distinct points
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document.write( "kx + y = 3     (1)\r\n" );
document.write( "x² + y² = 5    (2)\r\n" );
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document.write( "Express y = 3-kx  from (1) and substitute it into (2). You will get\r\n" );
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document.write( "\"x%5E2+%2B+%283-kx%29%5E2\" = 5.\r\n" );
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document.write( "Simplify:\r\n" );
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document.write( "\"x%5E2+%2B+9+-+6kx+%2B+k%5E2x%5E2\" = 5,\r\n" );
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document.write( "\"%28k%5E2%2B1%29%2Ax%5E2+-6kx+%2B+9-5\" = 0,\r\n" );
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document.write( "\"%28k%5E2%2B1%29%2Ax%5E2+-+6kx+%2B+4\" = 0.\r\n" );
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document.write( "Discriminant \r\n" );
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document.write( "d = \"b%5E2+-+4ac\" = \"%286k%29%5E2+-+4%2A%28k%5E2%2B1%29%2A4\" = \"36k%5E2+-+16%2A%28k%5E2%2B1%29\" = \"36k%5E2+-+16k%5E2+-+16\" = \"20k%5E2+-+16\".\r\n" );
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document.write( "The condition for  \"kx+y=3 meets x²+y²=5 in two distinct points\"  is  this inequality  d > 0,  or\r\n" );
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document.write( "\"20k%5E2+-+16\" > 0,   or, which is the same (cancel the factor 4)\r\n" );
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document.write( "\"5k%5E2+-+4\" > 0,  or\r\n" );
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document.write( "|k| > \"sqrt%284%2F5%29\" = \"2%2Fsqrt%285%29\".\r\n" );
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document.write( "Answer.  kx+y=3 meets x²+y²=5 in two distinct points  if  and only if k < \"-2%2Fsqrt%285%29\"  OR  k > \"2%2Fsqrt%285%29\".\r\n" );
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