Answer
The force is reduced to 1/4 of its original value, no matter the sign of the original charges. Coulomb’s law defends our answer.
Work Step by Step
Use Coulomb's Law.
$$F = k \frac{q_{1} \; q_{2}}{d^{2}}$$
If d is doubled, the force is divided by a factor of 4.
This statement does not depend on the value or signs of the charges q.
