A charge distribution consisting of three point-charges q, -2q, and q located along the y-axis as shown below is called an electric quadrupole.
a) Find an expression for the electric field at a point P on the x-axis.
b) Graph the electric field for the case where q=9nC and d=1.75cm.
c) Show for large x (x>>d) that E=(1/4πε0)(3qd²/x4)"i hat"N/C