the answer
the complement of the question is
Find the interval on the real number line for which the radicand is nonnegative (greater than or equal to zero) so that the radical sqrt(8 x - 8) defines a real number. Leave answer in interval notation.
sqrt(8 x - 8) is definite function if 8 x - 8 ≥0,
8 x ≥ 8 and x ≥ 8/ 8 = 1, x ≥ 1, so the interval solution is [1, infinity[