Correct answer: (-1, 0) (0, 1)
The equation has no integral solutions when the quadratic expression in terms of the fractional part of x, which is bounded between 0 and 1, does not yield any real roots. The values of a must be such that the discriminant of the quadratic is negative, which occurs in the intervals (-1, 0) and (0, 1), ensuring that the equation cannot equal zero for any integer value.