You are waiting in the ticket line at a rock concert. originally you were 50 meters from the ticket booth and now you are only 5 meters away. what is your change in position?

here our distance is given with respect to ticket booth

initial distance is given 50 m from the booth

So our initial position is

now after this finally we reach at final position

now change in position is given as

so change in position is 45 m in magnitude and since we are coming closer to the booth so its coming negative in sign

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.