The line y = 1 is a horizontal line and thus is a line that is parallel to the x-axis.
If we reflect about a line that is parallel to the x-axis, then the x-coordinate of the point (that is reflected) will remain the same, thus the image of (-1, 5) has x-coordinate -1 and thus the point is of the form (-1, b).
The point (-1, 5) is 4 units from the line y = 1 (because the difference between y = 5 and y = 1 is 4).
The reflected point has to be the same distance from the line y = 1 as the original point
