Question

1. Write in factorial form. n(n-1)(n-2)...(n-r+1)2. (n-r)! = ?

Answer 1

2.

the answer is

$(n-r)!=1\cdot2\cdot3\cdot4\cdot\ldots\cdot(n-r-1)\cdot(n-r)$

Explanation

The factorial of a number is the multiplication of all the previous numbers of the number given, for example

$5!=1\cdot2\cdot3\cdot4\cdot5=120$