Prove that an Abelian group with two elements of order 2 must have a subgroup of order 4.
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Originally Posted by mandy123 Prove that an Abelian group with two elements of order 2 must have a subgroup of order 4. Take $\displaystyle \{e,a,b,ab\}$ where $\displaystyle a,b$ have order $\displaystyle 2$.