If that's the definition,
The difficulty is to show that which is true because has no occurence in the formula . (in the two cases, is either in or has to be in every )
I'm having some difficulty with these two problems,any help is appreciated.
1)Prove that given is not empty
Since B is not empty, let , then it follows , so LHS= such that . This doesn't look right, so anyone can help me figure out what I did wrong here.
2) Is it true that ? When does equality hold?
Here, can I take the empty set to be B, and the equality will be false because the empty set doesn't contain any element, but we need . Is my argument correct? I can't find condition such that equality holds.