f(x)的最高次项是x^(n+1),其余项的次数均低于(n+1)，n+1阶求导后均为0x^(n+1)一阶导数=(n+1)x^nx^(n+1)二阶导数=(n+1)nx^(n-1)...x^(n+1)n+1阶导数=(n+1)!x^(1-1)=(n+1)!∴f(x)=x(x-1)(x-2)...(x-n)的n+1阶导函数=(n+1)!
