## Precalculus (6th Edition) Blitzer

$A\cup B=\{a,b,c,d,e\}$
Recall that an element $x\in A\cup B$ if and only if $x\in A$ or $x\in B$. Thus, we find the union by finding the elements that are contained in either set $A$ or set $B$. This gives us $A\cup B=\{a,b,c,d,e\}$.