hello, i am having problems with this question

"If a force on an object is always directed along a line from the object to a given point, and the magnitude of the force depends only on the distance of the object from the point, the force is said to be a central force. Show that any central force is a conservative force."

i know that if you move an object around and place it back in its original position no energy is lost

i have wd= ma * d

however i would need to write ma as F ?

very stuck, thanks