The line y = 4 is a horizontal line in the Cartesian plane. The distance from any point( x, y) to this line is given by d = | y - 4| and this distance to be equal to k | y - 4 | = k case1, y - 4 = k, y = k + 4 ⇒ 4 + k case2, y - 4 = - k, y = - k + 4 ⇒ 4 - k combining the two solutions above, we have y = 4 \(\pm\) k