Showing whether a subgroup is normal
55493
Showing that the path-connected component of the identity matrix in a subgroup of $GL_n(\Bbb R)$ is a normal subgroup
151130
When is the product of $n$ subgroups a subgroup?
44165
the image of normal subgroups
45580
Intersection of conjugate subgroups is normal
113925
Normal Subgroup Counterexample
6134
Some Subgroup of Dihedral Group is Normal
58251
To show every sylow p-subgroup is normal in G
141265
Finding a normal and not normal subgroup of $S_3$
109236
Subgroups containing kernel of group morphism to an abelian group are normal.
20386
Any subgroup of index $p$ in a $p$-group is normal.
15630
Normal subgroup of prime order is characteristic
102622
K is a subgroup of G. Show that K is not a normal subgroup
37971
Prove that the center of a group is a normal subgroup
154398
Show that H is a subgroup of G
44152
If $G$ has only one subgroup of order $n$, then that Subgroup is Normal
124237
Group equals union of three subgroups
16804
Prove whether or not a subgroup is normal in the dihedral group $D_4$