The equation of the locus of a point which moves so as to be at equal distances from the point (a, 0) and the y− axis is
Replace (h, k) by (x, y), then y2−2ax+a2=0 is the required locus.
ABCD is a square, the length of whose side is a. Taking AB and AD as the coordinate axes, the equation of the
circle passing through the vertices of the square, is