Solution: The electric field intensity is the superposition of the electric field intensity of the three charges. To find the location of zero electric field intensity, we assume a location on the axis, say + x, calculate the electric field intensity, and set it to zero. However, there are four distinct domains that must be considered: Two are x > a and x < a. The other two domains are 0 < x < a and a < x < 0. Because the configuration of charges is symmetric, only two of these four domains need to be considered. Therefore, we solve for the domains x > a and 0 < x < a: