Question

How do I formally express the solution of `x! = x` when I know that `x = 1, 2 {x in NN}`?

The solutions are quite obvious but I don't know how I can write them down.

Answer 1

`1< x! = x rArr (x-1)! =1 rArr x-1 = 1`, and so, x = 2, besides x = 1

Explanation:

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