Answer:
A ∪ B = { 1,3,4,7,8,9}
Explanation:
U = {1,2,3,4,5,6,7,8,9,10}
A={1,3,4} B={4,7,8,9} and C={2,6,10}
UNION OF SETS:
Union of two sets is defined as the set which has all the elements from both the sets.
Also, REPETITION OF THE ELEMENTS in NOT allowed in union of sets.
Now, here:
A={1,3,4} B={4,7,8,9}
So, A ∪ B = { 1,3,4,7,8,9} ( element 4 is written only ONCE here)