Charges of 
are located at both 
and 
, and a charge
of 
is located at 
on the y-axis. This arrangement of
charge can be visualized as two opposing dipoles.
a) Find the electric field (magnitude and direction) at an arbitrary point on the x-axis.
b) What is nonzero term in the expansion of the electric field
evaluated far from the charges, i.e. - for 
? Your answer
should be a series of terms in inverse powers of 
.