Value Theorem 9. Use the Mean Value Theorem to prove that if f (x) is differentiable on [a, b] and f' (x) = 0 on [a, b] then f (x) is a constant 10. Use the Mean Value Theorem to prove that if f (x) and g(x) is differentiable on [a, b] and f' (x) = g'(x) also on [a, b]rthen f(x) - g(x) is a constant