document.write( "Question 983439: 1. IF X=7-4RT3, FIND THE VALUE OF RTX+1/RTX?
\n" ); document.write( "2. X=3+2RT2, FIND THE VALUE OF X^3-1/X^3?
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Algebra.Com's Answer #604324 by ikleyn(52800)\"\" \"About 
You can put this solution on YOUR website!

\n" ); document.write( "1. Let me re-formulate your first request in the correct algebraic form:\r
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\n" ); document.write( "\n" ); document.write( "      If  \"x\" = \"7-4sqrt%283%29\",  find the value   \"sqrt%28x%29\" + \"1%2Fsqrt%28x%29\".\r
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\n" ); document.write( "\n" ); document.write( "Solution\r
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\n" ); document.write( "\n" ); document.write( "We have  \"x\" = \"7-4sqrt%283%29\".  Let  \"y\" be  \"7%2B4sqrt%283%29\":  \"y\" = \"7%2B4sqrt%283%29\".\r
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\n" ); document.write( "\n" ); document.write( "Then  \"x%2Ay\" = \"%287-4sqrt%283%29%29\".\"%287%2B4sqrt%283%29%29\" = \"7%5E2\" - \"%284sqrt%283%29%29%5E2\" = \"49\" - \"16%2A3\" = \"49\" - \"48\" = \"1\".     (I applied here the formula \"%28a-b%29%2A%28a%2Bb%29\" = \"a%5E2+-+b%5E2\".   Are you familiar with it ?)\r
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\n" ); document.write( "\n" ); document.write( "Thus we obtain a remarkable formula: \"%287-4sqrt%283%29%29\".\"%287%2B4sqrt%283%29%29\" = \"1\". \r
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\n" ); document.write( "\n" ); document.write( "It means that the numbers  \"7-4sqrt%283%29\"  and  \"7%2B4sqrt%283%29\"  are reciprocal each to the other:  their product is equal to  1. \r
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\n" ); document.write( "\n" ); document.write( "In other words,  \"x\" = \"1%2Fy\",   or   \"y\" = \"1%2Fx\",     i.e.   \"1%2Fx\" = \"7%2B4sqrt%283%29\".\r
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\n" ); document.write( "\n" ); document.write( "Now,  let us square   \"sqrt%28x%29+%2B+1%2Fsqrt%28x%29\":\r
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\n" ); document.write( "\n" ); document.write( "\"%28sqrt%28x%29+%2B+1%2Fsqrt%28x%29%29%5E2\" = \"%28sqrt%28x%29%29%5E2\" + \"2%2Asqrt%28x%29%2A%281%2Fsqrt%28x%29%29\" + \"1%2F%28sqrt%28x%29%29%5E2\" = \"x\" + \"2\" + \"1%2Fx\".     (I applied here the formula \"%28a%2Bb%29%5E2\" = \"a%5E2+%2B2ab+%2B+b%5E2\".   Hope you are familiar with it.) \r
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\n" ); document.write( "\n" ); document.write( "Substitute here   \"x\" = \"7-4sqrt%283%29\"  and   \"1%2Fx\" = \"7%2B4sqrt%283%29\"  as we found above. \r
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\n" ); document.write( "\n" ); document.write( "You can continue this identity as \r
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\n" ); document.write( "\n" ); document.write( "\"%28sqrt%28x%29+%2B+1%2Fsqrt%28x%29%29%5E2\" = \"%28sqrt%28x%29%29%5E2\" + \"2%2Asqrt%28x%29%2A%281%2Fsqrt%28x%29%29\" + \"1%2F%28sqrt%28x%29%29%5E2\" = \"x\" + \"2\" + \"1%2Fx\" = \"7-4sqrt%283%29\" + \"2\" + \"7%2B4sqrt%283%29\" =   (now collect the common terms and annihilate the terms with  \"sqrt%283%29\" ): \r
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\n" ); document.write( "\n" ); document.write( "= 7 + 7 + 2 = 16.\r
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\n" ); document.write( "\n" ); document.write( "Since   \"%28sqrt%28x%29+%2B+1%2Fsqrt%28x%29%29%5E2\" = 16,  you get   \"sqrt%28x%29+%2B+1%2Fsqrt%28x%29\" = 4. \r
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\n" ); document.write( "\n" ); document.write( "Amazingly,  isn't?\r
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\n" ); document.write( "\n" ); document.write( "The solution is completed.\r
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\n" ); document.write( "\n" ); document.write( "The problem and the solution are like sweet cookies.  Thank you  (and yours teacher)  for giving it. \r
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\n" ); document.write( "\n" ); document.write( "2.  Regarding the second problem of your request,  try to solve it yourself similar to the first one.\r
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\n" ); document.write( "\n" ); document.write( "You have   \"x\" = \"3%2B2sqrt%282%29\".\r
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\n" ); document.write( "\n" ); document.write( "Introduce   \"y\" = \"3-2sqrt%282%29\".\r
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\n" ); document.write( "\n" ); document.write( "Check that   \"x%2Ay\" = 1,   i.e. the numbers   \"3%2B2sqrt%282%29\"  and   \"3-2sqrt%282%29\"  are reciprocal   and   \"1%2Fx\" = \"3-2sqrt%282%29\".\r
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\n" ); document.write( "\n" ); document.write( "Based on it,  complete the solution yourself.\r
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\n" ); document.write( "\n" ); document.write( "Good luck !!!\r
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