FACTORIAL n  
If n = 1,2,3, . . . factorial n or n factorial is defined as n! = 123 n We also define zero factorial as 0! = 1 

BINOMIAL FORMULA FOR POSITIVE INTEGER n  
If n = 1,2,3, . .. then This is called Binomial Formula. It can be extened to other vaues of n and then is an infinite series. 

BINOMIAL COEFFICIENTS  
where the coefficients, called binomial coefficients, are given by 

PROPERTIES OF BINOMIAL COEFFICIENTS  
This leads to Pascal Triangle. 

MULTINOMIAL FORMULA  
where the sum, denoted by ∑, is taken over all nonnegative integers n_{l}, n_{2}, . . .,n_{p} for which n_{1}+n_{2}+...+n_{p}=n 
