[(B′∪(B′−A))]′ =___
A
B
A - B
B - A
[B′∪(B′−A)]′=[B′∪(B′∩A′)]′ (∵A−B=A∩B′)=[(B′∪B′)∩(B′∪A′))]′=[B′∩(A∩B)′]′=(B′)′∪((A∩B)′)′ (∵(A∩B)′=A′∪B′)=B∪(B∩A)=B