Find the magnitude and direction of force in a dipole

[kelkel]

Homework Statement

In Figure 21.12, two point charges q1=3uC and q2=-3uC interact with a third point charge Q=7uC. Find the magnitude and direction of the total (net) force on Q.

Homework Equations

Edipole= kqs/r^3

The Attempt at a Solution

I solved for the electric field with the above equation. I then multiplies that by the charge of Q to get the net force but it won't work! Help!

 

[Doc Al]

That formula only applies at distances much greater than the distance between the charges of the dipole. Instead of using that formula, just find the force from each charge and add them up (vector addition, of course) to get the net force.