I think there is a parenthesis on the second half of the last line right? so that it distributes and makes positive? Then I know is equal to But i'm not sure how to prove it..
Do you know the distributive laws of union/intersection?
Yes, but I'm not sure how to apply it to that.. btw i left out a parenthesis..it should be . For the distributive laws i know that = . Is that what you're talking about?