Algebra of two equal positive charges

[Lisa...]

I need some help in finding a way to solve the following problems.:

- Two equal positive charges q are on the y axis, one at y= +a and the other at y= -a.

a) Show that the electric field on the x-axis is along the x-axis with
E_x= 2kqx(x² + a²)^-3/2.

b) Show that near the origin, when the x is much smaller than a, E_x is approximately 2kqx/a³.

c) Show that for values of x much larger than a, E_x is approximately 2kq/x². Explain why you would expect this result even before calculating it.

Thanks for your efforts!

 

[inha]

You need to show your efforts before you get help. So, where do you think you should start?