Use the definition of the derivative to show f'(x) = 2x + 2 if f(x) = x + 2x This means the long way by

Use the definition of the derivative to show f'(x) = 2x + 2 if f(x) = x² + 2x This means the "long way" by substituting into the limit: f'(x) = lim h?0 f(x+h)-f(x) / h