let H and K be subgroups of G. Prove that H U K is a subgroup iff either H is a subset of K or K is a subset of H?
just having trouble with this problem. appreciate a few pointers.
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i give u a hint
there will be 2 parts to this question.
Assume: is a subgroup. Think what happens when H is not contained in K or vice versa.
Converse: this is very easy. Take or . Since are subgroups the statement follows
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