Ignoring the sign of a charge in electromagnetism

[FatPhysicsBoy]

Homework Statement

I just did a question on a charge moving relative to a stationary charge from an initial position x₁ to a final position x₂. I was under the impression that for questions involving coulombs law, and the equations for Electric Field Strength, Force and Potential we ignore any -ve signs on charges?

So after checking my answer I saw that I had the right magnitude but the wrong sign. The only thing I did differently was take the charge in my equation for the potential as 4μC instead of -4μC as can be seen on line 4 of the calculation below.

Homework Equations

The Attempt at a Solution

Any insight into this will be greatly appreciated!

 

[FatPhysicsBoy]

Reserved.