Hello everyone, This is probably going to come off as a very silly question. However, I have not had calculus in several years. I was angry that my physics textbook did not have a derivation of Electric Potential Energy. So, I finally came across it, and I see that the integration of the work equation from some point, r_a to another point, r_b yields, kQq (1/r_a - 1/r_b). Can someone explain to me where, (1/r_a - 1/r_b) is coming from?