Ambiguous Electric-Field magnitude

[PHYHelp519]

Homework Statement

On the x axis, charge +Q lies at x = -a and charge -Q lies at x = +a. Point P lies on the axis at
x = +b, where b > a. a) Work out the electric field magnitude of P b) What is the direction of this …field?

Homework Equations

E=kqr/r3

The Attempt at a Solution

E=2kQa/(b2-a2) + 2kQa/(b2-a2)=
Ep=4kQab/(b^2 - a^2)^2. My teacher said that the solution was correct, however my work was not.
For b, I determined the direction to be to the right towards the negative charge.

I would appreciate any assistance.

 

[ehild]

Homework Statement

On the x axis, charge +Q lies at x = -a and charge -Q lies at x = +a. Point P lies on the axis at
x = +b, where b > a. a) Work out the electric field magnitude of P b) What is the direction of this …field?

Homework Equations

E=kqr/r3

The Attempt at a Solution

E=2kQa/(b2-a2) + 2kQa/(b2-a2)=
Ep=4kQab/(b^2 - a^2)^2. My teacher said that the solution was correct, however my work was not.
For b, I determined the direction to be to the right towards the negative charge.

I would appreciate any assistance.

The equation in red does not make sense. What are a2, b2? Do you mean that the contribution is the same from both charges?

ehild