Proving H is Normal in Finite Group with One Subgroup

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SUMMARY

If G is a finite group with exactly one subgroup H of a given order, then H is confirmed to be a normal subgroup. This conclusion arises from the properties of group actions and the uniqueness of the subgroup. Specifically, for any element g in G, the conjugate gHg^-1 remains equal to H, reinforcing its normality. This result is foundational in group theory and is applicable in various mathematical contexts.

PREREQUISITES
  • Understanding of finite group theory
  • Familiarity with subgroup properties
  • Knowledge of group actions and conjugation
  • Basic concepts of normal subgroups
NEXT STEPS
  • Study the properties of normal subgroups in finite groups
  • Explore the concept of group actions and their implications
  • Learn about the classification of finite groups
  • Investigate the implications of Lagrange's theorem in subgroup analysis
USEFUL FOR

Mathematics students, particularly those studying abstract algebra, group theorists, and educators looking to deepen their understanding of subgroup normality in finite groups.

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Homework Statement



If G is a finite group that has exactly one subgroup H of a given order, then H is normal.

Homework Equations



N/A

The Attempt at a Solution



I cannot figure out what makes a subgroup H special if it is the only one of a given order...
 
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Pick a g in G. What is the order of g-1Hg?
 

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