Let $P=\{A \subseteq \mathbb N: A$ is non-empty, finite and has an even number of elements$\}$. Consider $X=\{A \in P : 1 \in A\}$. Does $X$ have a lower bound in $(P,\subseteq)$?
I think that there is a lower bound.
Let $P=\{A \subseteq \mathbb N: A$ is non-empty, finite and has an even number of elements$\}$. Consider $X=\{A \in P : 1 \in A\}$. Does $X$ have a lower bound in $(P,\subseteq)$?
I think that there is a lower bound.
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Hint: consider $\{1,2\}$ and $\{1,3\}$.