A charge of -2q is placed a distance r from the origin and a charge of +2q is placed a distance 2r from the origin. What is the amount of work needed to move a charge of q to the origin from infinity?

Question

I don't get the question. And please explain to me how can I do it.

Answer 1

What is the potential energy of the charge q at the origin?

PotentialV=K(-2q)/r + K(2q)/2r=-kq/r

Work to take to infintity = Vq or
= -Kqq/r