I bought a used car from a dealer and found out that the car may possibly have been in a car accident, can I take it back and get my money back?

Nevada has no right of rescission period for automobile purchases.  While there is 3 day rescission period for door-to-door sales (NRS 598.230), obviously this statute would not apply to a sale from an automobile dealership.  Therefore there is no "catchall" rescission period for automobile sales. Nonetheless any automobile transaction that involves fraud in the inducement triggers the right of the defrauded party to seek rescission as a remedy. See Friendly Irishman v. Ronnow, 74 Nev. 316, 318 (1958).  The standard is different if the dealer made an affirmative misstatement of fact as opposed to omitting to tell you a material fact.   If you can prove that the Dealer lied to you about whether the car was in an accident and made an intentional misrepresentation of fact, in other words that the Dealer knew of the material fact and intentionally misrepresented the fact to you, then you can ask for rescission.  Such intentional misrepresentation of material facts in a contract, resulting in the intended deception, constitutes actual fraud, which is a proper ground for rescission of the contract.   Total reliance upon a misrepresentation is not required to entitle a party to rescission; it is enough that the misrepresentation is part of the inducement to enter into the transaction.   In fact the Nevada Supreme Court has held that even if you were negligent in your conduct in the transaction will not bar equitable relief of rescission if the misrepresentation was intentional and actually relied upon by you. The question then becomes whether as "As Is" disclaimer and failure to disclose a material fact rises to the level of intentional misrepresentation.  First, you would have to find out if the dealer had actual knowledge of the accident.   If the Dealer had actual knowledge, you would have to prove that the failure to disclose the fact of the accident (as opposed to an actual lie) rises to the level of fraud.  Generally, fraud is not found where there has been merely a nondisclosure unless you can demonstrate that the Dealer had a duty to disclose the fact at issue.