Mathematics I / Sets and Set-Builder Notation
Practice question · True or false

For A={1,2}A = \{1, 2\}, both 1A1 \in A and {1}A\{1\} \in A are true.

Hints
  1. What are the members of A?
  2. 1 is a member; {1}\{1\} is a subset.
Show the answer

False

Why

False. The members of AA are 1 and 2, so 1A1 \in A holds but {1}A\{1\} \in A does not, {1}\{1\} is a subset, written {1}A\{1\} \subseteq A. Membership and inclusion are different relations, and the distinction becomes essential once sets contain other sets.

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