Using the definition of the derivative, find f'(x). Then find f'(1), f'(2), and f'(3) when the derivative exists. f (x) = - x2+5x -4 f' (x) = (Type an expression using x as the variable.) Select the correct answer below and, if necessary, fill in the answer box to complete your choice. O A. f' (1) = (Type an integer or a simplified fraction.) O B. The derivative does not exist. Select the correct answer below and, if necessary, fill in the answer box to complete your choice. O A. f' (2) = (Type an integer or a simplified fraction.) O B. The derivative does not exist. Select the correct answer below and, if necessary, fill in the answer box to complete your choice. O A. f'(3) = (Type an integer or a simplified fraction.) O B. The derivative does not exist