Answer:
3 elements
Explanation:
Let A = solution set of x²-4
B = solution set of x²-3x+2
First, find the solution of each sets:

Set B:

Now we can write new set as:
A = {2, -2}
B = {1, 2}
The union of A and B means combine both sets together:
A ∪ B = {2, -2, 1, 2}
However, in a set, we do not write duplicate elements, so the union set will be:
A ∪ B = {2, -2, 1}
Hence, there are 3 elements in A ∪ B.