Moving three points infinitely away

[phunphysics2]

U=kqoq/r ?

Please look at the attachments. I was wondering if someone could please check my work. That is all.

Thank you for your time!

 

[SammyS]

U=kqoq/r ?

Please look at the attachments. I was wondering if someone could please check my work. That is all.

View attachment 55488

View attachment 55489

Thank you for your time!

Why did you square the distances?

How did you come up with the signs?

 

[phunphysics2]

Sorry about the squaring in thr pic. I erased them after I took the pic.
I checked with the answer key and my answer matched.
Thank you for your time and rapid response! :)