Oh,thanks Grandad at last i start to figure out how to do this type of question.thank you very much(Wink)Hello mayThis uses the Distributive Law:\(\displaystyle (P \cup Q)\cap (P \cup R) = P \cup (Q \cap R)\)where I have replaced \(\displaystyle P\) by \(\displaystyle B'\), \(\displaystyle Q\) by \(\displaystyle \oslash\) and \(\displaystyle R\) by \(\displaystyle A'\).

Yes, I'm rather afraid that you do. As I said - you'll need lots of practice!

Grandad

PS ... and to answer your extra question, following your edit:

\(\displaystyle \oslash \cap A' = \oslash\) uses what I have always known as anIdentity Law, but others sometimes refer to as aDomination Law.

See, for example, here.

erm i want to ask another question..same topic do i need to put the question in new thread or at here?