Question

proof for 0!(zero factorial)=1 .

Answer 1

n!=n(n-1)! ; put n= 1 ; 1! = 1(1-1)! ; 1 = 0!, (1! = 1)

Answer 2

The factorial of a number is defined as:

n!=n∗(n−1)∗(n−2)∗(n−3)∗...∗1

So:

5!=5∗4∗3∗2∗1=120

4!=4∗3∗2∗1=24

Hence, it can be observed that :

n!=n∗(n−1)!

From this equation, substituting 1 for n:

1!=1∗(1−1)!

1!=1∗0!

0!=1/1

0!=1