Union and Intersection of Sets

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I need help figuring out how to find the Union or intersection of sets when provided with inequalities.

For example:
Find the intersection of sets {xlx<9},{xlx<-8}
Find the Union of sets {xlx<9}, {xlx<-8}

Thank you!

In: 0

The intersection would be all values of x that is true for both statements and the union would be all values of x that is true for at least one of the statements.

Say you have two sets: {3, 6, 9} and {4, 6, 8}

The intersection of them would just be {6}, since that’s the only value in both

The union would be {3, 4, 6, 8, 9} since that all unique values in at least one of them

When given sets like these what I would do is to mark them on the numberline this perfectly visualises the problem. The part you marked twice is the intersection and the parts you marked altogether is the union.