Step 1: Find the union of sets A and B, A∪B.
A∪B={1,2,5,6,7}∪{1,3,4,5,6,8}
A∪B={1,2,3,4,5,6,7,8}
Step 2: Find the complement of A∪B, denoted as (A∪B)′. This includes all elements in the universal set U that are not in A∪B.
U={1,2,3,4,5,6,7,8,9}
(A∪B)′=U−(A∪B)
(A∪B)′={1,2,3,4,5,6,7,8,9}−{1,2,3,4,5,6,7,8}
(A∪B)′={9}
Step 3: Find the complement of set A, denoted as A′. This includes all elements in U that are not in A.
A′=U−A
A′={1,2,3,4,5,6,7,8,9}−{1,2,5,6,7}
A′={3,4,8,9}
Step 4: Find the complement of set B, denoted as B′. This includes all elements in U that are not in B.
B′=U−B
B′={1,2,3,4,5,6,7,8,9}−{1,3,4,5,6,8}
B′={2,7,9}
Step 5: Find the intersection of A′ and B′, denoted as A′∩B′. This includes all elements common to both A′ and B′.
A′∩B′={3,4,8,9}∩{2,7,9}
A′∩B′={9}
Step 6: Compare the results from Step 2 and Step 5.
We found (A∪B)′={9} and A′∩B′={9}.
Since both sides are equal, the statement is proven.
(A∪B)′=A′∩B′