Consider three charges placed in a straight line, Charges q_a and q_b are separated by 2.00 meters. The magnitude of the charges A and B are, q_a= 45.0 C; and q_b= -5.00 C. The charge is q_chas a small but unknown charge.

Show that the only location where q_ccan experience a zero net force is in the region to the right of both charges. Show that both the magnitude and sign of q_c do not affect this result. The first two elements of this problem, the general location, and the sign/magnitude involve little or no calculation or even numerical data.

I can't figure out how to get started, please help.