We will consider the electric field at points to the right and left and 3 cm above or below the midpoint. We have chosen to focus on points A, B, C, D for this problem which will explore how the symmetry of the charge distribution can be used to simplify calculations.
Electric fields go away from positive charges and toward negative charges.
The closer the point is to the charge, the larger the electric field. Consider these symmetric points. Take advantage of symmetry to save yourself as much work as possible. Thus The y component is zero by symmetry.