How can you tell if the force is attractive or repulsive in electrostatics?

The electrostatic force of attraction or repulsion is can be found as follows,

let us consider 2 bodies in gravitational field of earth. Let the distance between those two bodies is equal to r meters. The charge on the first body is Q1 and charge on second body is Q2.

By columbs force, F α Q1*Q2

r²

F=k Q1*Q2 where k-gravitational constant.

r²

Ask me, if you have any doubt regarding this.

If charges have same sign force is repulsive

If charges have different signs force is attractive