2x!=x! * x => x=2 ; just mentally imagining this; okay full computation: 1/2x^2(x-1)!(x-2)!=x!; then x(x-1)!x(x-2)!=2x!; x!x(x-2)!=2x!; x(x-2)!=2; where 0!=1 and 2*1{2-2}=2

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