jerry79
Member

Last Monday the teacher explained to us the concept of “factorial”. I don’t get it.

2plus2
Member

Simply stated, the factorial of ANY given integer is simply the product of all its prior integers starting with 1 leading up to AND including the given integer itself.
Examples….
3!=1x2x3
6!=1x2x3x4x5x6

philippgrinev
Member

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*…*(n3)*(n2)*n – this is very much like n!, but here we miss out, as I tried to show, the number n1. 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!/(n1). Hope you understand the logic now! If you have any more questions, feel free to email me at filippgrinyov@yandex.ru
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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
