I do not understand the process of separating variables such as in derivatives. I thought that dy/dx is just the rate of change of y with respect to the independent variable x. Why can you physically move dx (like multiply it on both sides)?? What would "dy" be reffered to as then? Simply the change in y? I also to not get why dx, dy, dt, etc. are used in integrals when it is just (with respect to). They seem to be variables now instead of simply definitions. Please help me understand why we can separate variables and just everything related to it in general. (I'm only in High School btw, so please don't use abstruse terms or concepts) Thanks.