Let A = {a, b, c}, B = {b, c, d, e} and = {c, d, e, f} be subsets of U = {a, b, c, d, e, f}. Then verify that:
(i) (A’)’ = A
(ii) (A ∪ B)’ = (A’ ∩ B’)
(iii) (A ∩ B)’ = (A’ ∪ B’)
(i) A’ = {d, e, f}
(A’)’ = {a, b, c} = A
Hence proved
(ii) AB = {a, b, c, d, e}
(AB)’ = {f}
A’ = {d, e, f}
B’ = {a, f}
A’B’ = {f}
(A
B)’ = (A’
B’)
Hence proved
(iii) A’B’ = {a, d, e, f}
AB = (b, c}
(AB)’ = {a, d, e, f}
(A
B)’ = A’
B’
Hence proved