At what distance along the central perpendicular axis of a uniformly charged plastic disk of radius 0.390 m is the magnitude of the electric field equal to one-half the magnitude of the field at the center of the surface of the disk?

two charges are fixed in place on the x-axis as shown. the charge at x = 0 is negative and has magnitude q = 2 μcoulombs (1 μcoulomb = 10-6 coulombs). the charge at x = d, (d = +12 cm), is positive and has magnitude q = 4 μcoulombs. find a point x = xo along the x-axis at which the electric field is zero.

the answer is f1 and d2 because if you put equal force on those two points the beam would balance trust me on this