It is used in informal spoken English, and is an abbreviation of "don't you." It would only be written that way to try to show that person was talking in a careless way. Example: You know how to speak English, don't cha? The speaker is expecting that the listener can speak English, and the "don't cha" part indicates that he wants the listener to verify this.

It is the slang for "Do not you?" or more commonly said "Do you not?" as in "You have a car, don't cha?" "You have a car, don't you?" or "Is that correct?".

Yes, this is a spoken form... once you squash up all the sounds, it's much easier to say "don't cha?" than "don't you"? (this happens a lot in English... a bit like making 'terima kasih' into 'makasih') And yes, it indicates a pretty careless way of speaking to us.

the two guys have the correct answer i agree so it will be answer to. cowboy...