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+3x-6 . . . 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