Answer
$\bar A\cup \bar B=\{0,1,2,3,5,6,7,8,9\}$
Work Step by Step
The given sets are
$A=\{1,3,4,5,9\},B=\{2,4,6,7,8\}$ and $U=\{0,1,2,3,4,5,6,7,8,9\}$
The symbol $ \bar {A}$ means the set containing the elements of the union set not in set $A$.
$ \bar {A} =\{0,2,6,7,8\}$
The symbol $ \bar {B}$ means the set containing the elements of the union set not in set $B$.
$ \bar {B} =\{0,1,3,5,9\}$
The symbol $\cup$ means the set containing all the elements of the given sets.
$\bar A\cup \bar B=\{0,1,2,3,5,6,7,8,9\}$
Hence, the answer is $\bar A\cup \bar B=\{0,1,2,3,5,6,7,8,9\}$.
