r is cumbersome and we need a notation which will help to reduce the size of this expression. The symbol n ! (read as factorial n or n factorial ) comes to our rescue. In the following text we will learn what actually n !
means. . . Factorial notation The notation n !
represents the product of first n natural numbers, i.e., the product × × × . . . × ( n – ) × n is denoted as n !.
We read this symbol as ‘ n factorial’. Thus, × × × . . .
Clearly, for a natural number n n ! = n ( n – ) ! = n ( n – ) ( n – ) ! [provided ( n ≥ )] = n ( n – ) ( n – ) ( n – ) !
[provided ( n ≥ )] and so on. MATHEMATICS Example Evaluate (i) ! (ii) ! (iii) !
– ! = – = . Example Compute (i) ! !