Answer: If A ⊂ B, then A = B \ ( B \ A)
ok, when you do B \ A, you are subtracting all the elements in A∩B from B. So the only elements remaining are those who aren't in A.
If we subtract this of B again, we are subtracting of B all the elements that aren't in A, so the only elements remaining are those who belongs in A.
If A ⊂ B then A U (B \ A) = B.
Again, when you do B \ A you are extracting all the elements that belongs to the A∩B from B. So you are extracting al the elements from A. and when you add all the elements of A again, then you recuperate B.
if AnC = AnC does not imply that B = C.
if A = {1,2}, B = {1,2,3,4,5} and C = {1,2,3}
then AnC = {1,2} and AnB = {1,2} but B and C are different.
