证明C(r+1,n)+ 2C(r,n)+C(r-1,n) = C(r+1,n+2)
问题描述:
证明C(r+1,n)+ 2C(r,n)+C(r-1,n) = C(r+1,n+2)
答
可以根据C(r+1,n)+C(r,n)=C(r+1,n+1)证明.
C(r+1,n)+ C(r,n)+ C(r,n) + C(r-1,n) = C(r+1,n+1) + C(r,n+1) = C(r+1,n+2)