document.write( "Question 1208298: if (x/y) + (y/x) = 1 , then y'' = (y/x) (True or False) \n" ); document.write( "
Algebra.Com's Answer #846629 by ikleyn(52787)\"\" \"About 
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\n" ); document.write( "if (x/y) + (y/x) = 1 , then y'' = (y/x) (True or False)
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document.write( "Let's investigate which  (or what)  function y(x) can be.\r\n" );
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document.write( "We have\r\n" );
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document.write( "    \"x%2Fy%29\" + \"y%2Fx\" = 1.\r\n" );
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document.write( "Let  z = \"y%2Fx\".  Then\r\n" );
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document.write( "    \"1%2Fz\" + z = 1,\r\n" );
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document.write( "    1 + z^2 = z,\r\n" );
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document.write( "    z^2 - z + 1 = 0,\r\n" );
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document.write( "    \"z%5B1%2C2%5D\" = \"%281+%2B-+sqrt%281+-+4%29%29%2F2\" = \"%281+%2B-+i%2Asqrt%283%29%29%2F2\".\r\n" );
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document.write( "So,  \"y%2Fx\"  has the constant value  \"z%5B1%5D\"  or  \"z%5B2%5D\".  Hence,\r\n" );
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document.write( "    y = z*x,  where  z is one of the two complex numbers  z = \"z%5B1%5D\" = \"%281+%2B+i%2Asqrt%283%29%29%2F2\"  or  z = \"z%5B2%5D\" = \"%281+-+i%2Asqrt%283%29%29%2F2\".\r\n" );
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document.write( "It implies\r\n" );
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document.write( "    y' = z = const  and then  y'' = 0.\r\n" );
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document.write( "Thus we have to compare, from one side,  y'' = 0  and, from the other side,  \"y%2Fx\" = \"z%5B1%5D\" or \"z%5B2%5D\",  what are not zero.\r\n" );
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document.write( "        So, the answer to the problem's question is  \"highlight%28highlight%28FALSE%29%29\".\r\n" );
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document.write( "But an interesting fact, which is worth to be noticed, is that  y' = z = \"y%2Fx\"  has one of the two possible constant values\r\n" );
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document.write( "\"%281+%2B+i%2Asqrt%283%29%29%2F2\"  or  \"%281+-+i%2Asqrt%283%29%29%2F2\".\r\n" );
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