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,…

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