here's another relation:
1) find the first derivative f'(x) for the function f(x) from first principles
2) find the second derivative by the definition of the derivative
3) find the third derivate, using the definition of the derivative
etc.
the nth derivative should turn out to be
lim {h->0}[ SUM {k=0 to n} [(-1)^(n-k)]*(n C k)*f(x+kh) ]/h^n