Binomial distribution implementation

void binomial()
{
int n,x;
double p;
printf("binomial distribution implementation:\n");
printf("enter n,x,p");
scanf("%d%d%lf",&n,&x,&p);
if(x>0)
printf("\npmf=%.3lf",(fact(n)/(fact(x)*fact(n-x)))*pow(p,x)*pow((1-p),(n-x)));
printf("\nmean=%.3lf \t variance=%.3lf",n*p,n*p*(1-p));
}
void neg_binomial()
{
int y,k;
double p;
printf("negative binomial distribution:\n");
printf("enter y,k and p for kth success (y>k)");
scanf("%d%d%lf",&y,&k,&p);
if(y>k)
printf("pmf=%.3lf",(fact(y-1)/(fact(k-1)*fact(y-k)))*pow((1-p),(y-k))*pow(p,k));

}