9.20做题记录

c(m,n)=m!/[n!*(m-n])!]

c(m,n)=c(n-1,m-1)+c(n,m-1)

c(m,n)=c(m-n,m)

(m+n)%p=(m%p+n%p)%p

(m-n)%p=(m%p-n%p+p)%p

(m*n)%p=(m%p*n%p)%p

(m/n)%p=(m%p*n^p-2%p)%p

(jc[n]%mod*(ql(jc[m]*jc[n-m],mod-2)%mod))%mod