document.write( "Question 935306: Find the value of n for which Un has the given value:
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Algebra.Com's Answer #568617 by Edwin McCravy(20060)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "\"U%5Bn%5D=%28n%2F%28n%2B4%29%29%28-1%29%5En\" where \"U%5Bn%5D=+7%2F9\"\r\n" );
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document.write( "\"7%2F9=%28n%2F%28n%2B4%29%29%28-1%29%5En\"\r\n" );
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document.write( "\"7%28n%2B4%29=9n%28-1%29%5En\"\r\n" );
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document.write( "\"7n%2B28=9n%28-1%29%5En\"\r\n" );
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document.write( "if n is odd, \"%28-1%29%5En=-1\"\r\n" );
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document.write( "\"7n%2B28=9n%28-1%29\"\r\n" );
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document.write( "\"7n%2B28=-9n\"\r\n" );
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document.write( "\"28=-16n\"\r\n" );
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document.write( "\"28=-16n\"\r\n" );
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document.write( "\"n=28%2F%28-16%29\", \r\n" );
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document.write( "\"n=-7%2F4\", not a non-negative integer, \r\n" );
document.write( "so there is no solution for n being odd.\r\n" );
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document.write( "so n must be even, \"%28-1%29%5En=1\"\r\n" );
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document.write( "\"7n%2B28=9n%281%29\"\r\n" );
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document.write( "\"7n%2B28=9n\"\r\n" );
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document.write( "\"-2n=-28\"\r\n" );
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document.write( "\"n=28%2F2\"\r\n" );
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document.write( "\"n=14\"\r\n" );
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document.write( "Checking:\r\n" );
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document.write( "\"U%5Bn%5D=%28n%2F%28n%2B4%29%29%28-1%29%5En\"\r\n" );
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document.write( "\"U%5B14%5D=%2814%2F%2814%2B4%29%29%28-1%29%5E14\"\r\n" );
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document.write( "\"U%5B14%5D=%2814%2F18%29%281%29\"\r\n" );
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document.write( "\"U%5B14%5D=7%2F9\"\r\n" );
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document.write( "That checks:\r\n" );
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document.write( "Answer: \"n=14\"\r\n" );
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document.write( "Edwin

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