Normal Subgroups of G: K ∩ N is Normal

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SUMMARY

The discussion focuses on proving that the intersection of two normal subgroups, K and N, of a group G is also a normal subgroup of G. It establishes that for any element h in the intersection K ∩ N and any arbitrary element g in G, the conjugate g^{-1}hg must also belong to K ∩ N. This is achieved by demonstrating that g^{-1}hg is in both K and N, leveraging the properties of normal subgroups.

PREREQUISITES
  • Understanding of group theory concepts, specifically normal subgroups.
  • Familiarity with group operations and conjugation.
  • Knowledge of set theory, particularly intersections of sets.
  • Basic proficiency in abstract algebra notation and terminology.
NEXT STEPS
  • Study the properties of normal subgroups in group theory.
  • Learn about the concept of group conjugation and its implications.
  • Explore examples of normal subgroups in specific groups, such as symmetric groups.
  • Investigate the implications of subgroup intersections in abstract algebra.
USEFUL FOR

This discussion is beneficial for students and educators in abstract algebra, particularly those studying group theory and normal subgroups. It is also useful for mathematicians seeking to deepen their understanding of subgroup properties.

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Homework Statement



Show that if K and N are normal subgroups of G, then K intersect N is normal to G.

Homework Equations





The Attempt at a Solution


K and N are normal.
Then:
gkg^-1 is in K
gng^-1 is in N
want to show the intersection is a normal subgroup of G.
My problem is how to deal with the intersection
 
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Take a h\in K\cap N (what does this mean?) and take an arbitrary g.
You'll need to show that g^{-1}hg\in K\cap N (so, what do you need to show?)
 
Take a h in the intersection of two normal subgroups is what that means
 

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