I think when we talk about negative or positive of a displacement, we mean that the direction of this displacement which is either going downward or upward. But my question is how about when it says +/-velocity. Does it mean the direction or it means it speeds up or slows down? I think velocity is influenced by displacement according to the formula? so it must be influenced by the sign (+/-) of a displacement. Same happens to acceleration? +/- a. How can i know they mean the direction or speeds. Thanks a lot.