Generalized Mean-Value Theorem: Let f and g be two functions, each having a derivative (finite or infinite) at each point of an open interval (a, b) and each continuous at the endpoints a and b. Assume also that there is no interior point a at which both f'(x) and g'(x) are infinite. Then for some interior point c we have f'(c)[g(b) – g(a)] = g'(c)[f(b) – f(a)].