document.write( "Question 1179318: Hi! I would like to ask some help regarding this question, where I need to find n. \r
\n" ); document.write( "\n" ); document.write( "nP4 = 28 {(n - 1)P2)}\r
\n" ); document.write( "\n" ); document.write( "I tried trial and error but it looks like it's a big number, it would really mean a lot if you help me. Thank you! \n" ); document.write( "

Algebra.Com's Answer #808845 by ikleyn(52781) $\"\"$ $\"About$

You can put this solution on YOUR website!
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document.write( "    nP4     =  n*(n-1)*(n-2)*(n-3).\r\n" );
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document.write( "    (n-1)P2 =  (n-1)*(n-2).\r\n" );
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document.write( "Therefore, your equation is\r\n" );
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document.write( "    n*(n-1)*(n-2)*(n-3) = 28(n-1)*(n-2),   assuming  n >= 4.\r\n" );
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document.write( "Cancel the factors  (n-1)  and  (n-2)  in both sides\r\n" );
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document.write( "    n*(n-3) = 28.\r\n" );
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document.write( "You can solve it formally as a quadratic equation, or can guess the solution mentally in two seconds:  n = 7.\r\n" );
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document.write( "ANSWER.   n = 7.\r\n" );
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