Are NP or P closed under subtraction? Im having a hard time deciding whether they are or aren't.Question was editedOriginal question:Im having some hard time figuring out what languages are closed under subtraction.Say you have 2 languages A, B  NP. Is A\B  NP? what about P?Commenters:My original question was extremely not accurate so i rephrased :)Thanks!
Complexity classes that are closed under subtraction
complexity theory;closure properties;np
$A \setminus B$ is defined as $\{x | x \in A ~ and ~ not ~ x \in B \}$. If you know the complexity of checking $x \in A$ and $x \in B$, what does that tell you about the complexitty of $x \in A \setminus B$? Can you see the algorithm for checking it?