y=(x-1)(x-2)(x-3)(x-4)...(x-n)

y=(x-1)(x-2)(x-3)(x-4)...(x-n)
y=(x-1)(x-2)(x-3)(x-4)...(x-n)

y=(x-1)(x-2)(x-3)(x-4)...(x-n)
Y是n次多项式呀.y(n+1)=n!
但这里X可为任意实数,不一定得是整数.

A(n,m)=n(n-1)(n-2)……(n-m+1)= n!/(n-m)!
Y = A(x,n+1)