Three charges +Q, q, + Q are placed respectively, at distance, 0, d/2 and d from the origin, on the x-axis.Three charges +Q, q, + Q are placed respectively, at distance, 0, d/2 and d from the origin, on the x-axis. If the net force experienced by + Q, placed at x= 0, is zero, then value of q is : (1) +Q/2 (2) –Q/2 (3) –Q/4 (4) +Q/4