October 1st, 2014, 05:57 PM  #11 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs  We really don't have an official policy here regarding making an effort, but yes on the other boards I admin, I would have slung the ban hammer some time ago. Last edited by MarkFL; October 1st, 2014 at 06:00 PM. 
October 2nd, 2014, 01:46 AM  #12 
Newbie Joined: Sep 2014 From: iasi Posts: 3 Thanks: 1 
4(n+1)!=(n)!(2n6)! Divide both sides by (n)! 4(n+1)! /(n)!=(2n6)! Simplify the left hand side: 4n+4 = (2n6)! Trial and error: minimum valid n value: 4. trying n=4: 20 = 2 False trying n=5: 24 = 4! > 24 = 24 True n=5 is the solution. Its uniqueness is guaranteed because the rate of change of the factorial (on the right) is greater than that of the linear function (on the left of the equal sign), for any integer greater than 5. 

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determining, equation, factorial 
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