Solving for force in vectors of Electric Field

[ltruiz45]

Homework Statement

The net force on the 1.0 charge in the figure is zero.
What is q?

Homework Equations

Please see attachment for question and image.

The Attempt at a Solution

I believed you would solve F =K|q1q2|/r2

 

[MisterX]

Write out the components of force that would be from each other particle on the center particle. Then set the sums for each component (one sum for up/down, one sum for left/right) equal to zero.

Or, first observe symmetry in the problem and realize one of these net force components is zero regardless of q.