As you have just started factorials, I believe you only need to know about the factorials of positive integers. The factorial of a positive integer is all the integers from 1 all the way to that integer inclusive multiplied together. So n! = 1*2*3*…*n.
From this definition, we can also simplify many expressions involving factorials, e.g. 1*2*3*4*…*(n-3)*(n-2)*n – this is very much like n!, but here we miss out, as I tried to show, the number n-1. But then, as we miss it in a product, we can just divide that product by what we miss! So we can write that as n!/(n-1). Hope you understand the logic now! If you have any more questions, feel free to e-mail me at email@example.com
If I do get marked as the best solver (which you can do by selecting it on my comment), I will certainly remember that I should use a similar tone and approach in future for people to understand me better, thank you for the potential feedback.
“If people do not believe that mathematics is simple, it is only because they do not realize how complicated life is.
― John von Neumann
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