The locus consists of 2 parallels to the given line with a distance of 4.
The equation of the given line is:
Now use the formula to calculate the distance of a point P(s, t) to a straight line:
The distance of point P(x, y) to the given line is therefore:
The locus is the perpendicular bisector of the line segment AB.
Let P have the coordinates (x, y). Calculate the distance AP and the distance BP. Both must be equal. Solve for y.