Battery positive negative

If you are talking about the power connector on the side of the computer, generally the center pin is the positive lead.

Why do you need to know?

If you are looking for a new charger, just look at the markings on your old charger.
If you are looking at the battery terminals, don't mess with them. Not all are for power.
You can just use a multimeter on the battery terminals to check the terminals you suspect as the power ones.