3) Let f'be the function given by (x-1)(x²-4). For what positive values of a is f continuous for all real numbers x? 2 x-a (A) none (B) 1 only (C) 2 only (D) 4 only (E) 1 and 4 only

But if a = 4, then we will have a removable discontinuity since the x^2 - 4 in the numerator will cancel with the x^2 - 4 in the denominator leaving f(x) = x - 1 with holes at (2, 1) and (-2, -3).  There is no information given that the function is defined at those points, so it remains discontinuous, right?