Two point charges, each of charge Q, are located on the x axis as shown in Figure P17.50...

Two point charges, each of charge Q, are located on the x axis as shown in Figure P17.50. A test charge is placed on the y axis a distance from the origin. (a) Where could you place another charge on the x axis so as to make the electric field zero at ? (b) Find the value of in terms of Q and .