If I need to prove that something is a subgroup and I say that are elements in the subgroup, will constructing a Cayley table with show that the subgroup is closed?

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- October 22nd 2009, 06:34 PMsfspitfire23Cayley table and subgroup
If I need to prove that something is a subgroup and I say that are elements in the subgroup, will constructing a Cayley table with show that the subgroup is closed?

- October 22nd 2009, 06:58 PMaliceinwonderland
- October 22nd 2009, 07:34 PMsfspitfire23
so it will also show associativity right?

- October 22nd 2009, 09:52 PMaliceinwonderland
To show that H is a subgroup of (G, *), it suffice to show that for all a and b in H (as a subset of G), . This basically checks the closure of an operation '*' and its existence of an inverse in H. If H satifies this subgroup condition, it means H also satisfies the remaining group axioms (identity, associativity). You can think that "associativity" w.r.t '*' is simply inherited from G.