f(x) = 1/((1-x)^2),在x=0进行泰勒展开? f(0) = 1, f'(x) = 2/((1-x)^3),so f'(0) = 2, f''(x) = 2*3/((1-x)^4),so f''(0) = 6, f(x)的n阶导数= (n+1)!/((1-x)^(n+2)),so f(x)的n阶导数在0点取值 = (n+1)!, f(x) = Sigma[(n+1)!*(x^n)],
