1/(x-1)=(x-1)^(-1)一阶导：-(x-1)^(-2)二阶导：2(x-1)^(-3)三阶导：-3×2(x-1)^(-4)……n阶导：[(-1)^n]n!(x-1)^(-n-1)=[(-1)^n]n!/(x-1)^(n+1),
