calculus – Trying to prove a series converges conditioanlly on R and on -R

Im trying to prove that there is a series enter image description here that converges conditionally on x = R1 and on x = -R1, im trying to think of an “an” series, i thought about leibniz series, or another series that is defined with an “-” inside it, but after couple of long hours trying to solve it, i would be glad to get an hint or direction to the solution!
thank you very much in advance!