2.1. Write each of the following explicitly:
{1} x {1,2} x {1,2,3}:
This is a Cartesian product of three sets. We can write it as:
$\{(1,1,1), (1,1,2), (1,1,3), (1,2,1), (1,2,2), (1,2,3)\}$
0 x {1,2}:
This is an empty set, since 0 is not a set. We can write it
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