In Fig. 21-28, particle 1 of charge and particle 2 of charge are held at separation on an x axis.

In Fig. 21-28, particle 1 of charge and particle 2 of charge are held at separation on an x axis. If particle 3 of unknown charge is to be located such that the net electrostatic force on it from particles 1 and 2 is zero, what must be the (a) x and (b) y coordinates of particle 3?