Easy# Set Theory: Union of Sets, Definition and Examples

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The union of two sets $A$ and $B$ is the set of elements that are either in $A$ or in $B$ or in both $A$ and $B$.

In other words, the unions of two sets $A$ and $B$ is the set of elements that are in at least one of $A$ and $B$.

The notation for the union of two sets $A$ and $B$ is $A\cup B$ or $A\bigcup B$ (just a bigger $\cup$ symbol). In set notation, we have:

$$A\cup B=\{x\mid x\in A \;{\rm or}\;x\in B\}$$

Which of the following is FALSE?