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**Electric Dipole and Electric Potential.. and binomial approximation!!**

## Homework Statement

An electric dipole at the origin consists of two charges +q and -q spaced distance s apart along the y-axis.

a.)Find an expression for the potential V(x,y) at an arbitrary point in the xy-plane.

b.)Use the binomial approximation to simplify your result of part A when s<<x and s<<y.

## Homework Equations

V=kq

_{1}/r

_{1}+kq

_{2}/r

_{2}

binomial approximation: (1+z)

^{n}=(1+nz) when z<<1

## The Attempt at a Solution

Solution to a is:

V = kq(1/(x

^{2}+(y-s/2)

^{2})

^{1/2})-1/(x

^{2}+(y+s/2)

^{2})

^{1/2}))

I just have no idea how to make the square root parts into (1 + something small)

^{1/2}

I multiplied out, and ended up with (just for the first fraction):

1/(x

^{2}+y

^{2}+s

^{2}/4)

^{-1/2}because i figured the -ys that came from expanding the (y-s/2)

^{2}is small enough to be considered zero.

Just a few hints to send me in the right direction would be awesome!