A and B are two variable points on x and y axes such that OA + OB = 1/2. Then the locus of the foot of the perpendicular from the origin on the line AB is
2(x2 + y2) (x+y) - xy = 0
2(x2 + y2) (x+y) + xy = 0
2(x2 + y2) (x+y) - 2xy = 0
2(x2 + y2) (x+y) + 2xy = 0