(3x 2 –27)/(x – 3) = 0 => (x 2 –9)/(x – 3) = 0 => (x 2 –9)= (x + 3)(x – 3) = 0以及(x – 3) ≠ 0 => x = -3或者3以及x ≠ 3,所以 x = -3 .