Given:
The charge

The charge q1 is located at

The charge

The charge q2 is located at x2 = 0
The charge

The charge q3 is located at

To find the net force on charge q3.
Step-by-step explanation:
The force on charge q3 due to q1 is

The force on the charge q3 due to q2 is

The forces acting on q3 can be represented as
Thus, the net force will be

The direction of the force will be negative as it lies on the negative x-axis.