In my website i don't need the price information so how to do to hide the price from BO when adding a new product?? and if i make the price attribute optional is there a problem in the core of magento please i need your advice and your experience in that thanks in advance
I don't see why you'd ever want or need to disable the price attribute on products. It would be a lot of work requiring you to overwrite multiple core classes and make changes to the database.
Also, you would never be able to do Magento updates, as they most likely wouldn't work with the changes and would end up breaking your site.
Just set all your products to $0.00 and hide the price on the frontend if you need to.