Locus of a point equidistant from two fixed points is the perpendicular bisector of the straight line joining the points Gradients of PQ = (5-3 / 3-1) = 2/2 = 1
Gradient bisector = -1
Equation of perpendicular bisector y - y1 = m(χ - χ1 y - 4 = -χ + 2 y = -χ + 6