Calculate Electric Potential Change: +1 & -3 Micro-Coulombs

[skt1BOXER]

Homework Statement

There is a +1 micro-coulomb charge at the origin and a -3 micro-coulomb charge at 2 meters away along the x-axis. I am suppose to find the change in Voltage if second charge is moved to 4 meters away from the origin.

Homework Equations

I am thinking of using delta V= - integral of E(x)dx , where the limits of integration is from 2 to 4.

The Attempt at a Solution

i am not sure why the negative three micro-coulomb isn't included when using this equation. can someone explain why?

 

[blochwave]

Well I'll tell you're over complicating it. Pretty much the only equation you need is electric potential = somestuff / r

You don't even need to know what the somestuff is, only that potential is inversely proportional to r