If n ≥ 0 and f(x) is (n+1)-times differentiable on the open interval (a, x) and n times differntiable on the closed interval (a,x), then
n! denotes the factorial of n and Rn(x) is the remainder term.
The remainder term is the difference between the Taylor polynomial of degree(n) and the original function.
where ξ is some number from the interval [a, x].