I need help on how to do this problem: Carry out the calculation on the simplest quadrupole: Two point dipoles are oppositely oriented along the z-axis, separated by distance a. The potential due to one dipole is V = (p cos(theta) / (4pi epsilon r^2). The result I should get for the quadrupole is: V = a p (3 cos^2(theta) - 1) / (4 pi epsilon r^3). I may need to use tensors in here, but I don't know how to use them. Thanks.