Anything is impossible, isn't it? Don't you mean "anything is possible"?

1.Anything is impossible, isn't it? The general rule is when the main sentence, in this case "anything IS impossible" is affermative, the tag question has a negative form "ISN'T IT". 2.In the other case, if the main sentence is negative, for example "anything ISN'T impossible", the tag question has an affermative form "IS IT"? Ex. Anything isn't impossible, is it? In the tag question you find the helping verb of the main sentence, with the opposite form. Ex. You don't like pizza, do you? We are studying, aren't we? They played football, didn't they? There are some particularities, when you say: 1. I like cooking, the tag question is AREN'T I? Then: I like cooking, aren't I? 2.When you say: She could have read this note, couldn't she have? 3. They should have studied more time, should they have? And so on.