normal subgroup if
N^g = N
If G is abelian, all subgroups of G are
If G is abelian, all subgroups of G are normal subgroups
If G is a group, N≤ G, N≤Z(G) then N is
If G is a group, N≤ G, N≤Z(G) then N is a normal subgroup of G
If G a group N≤G, [G:N] = 2, then…
If G a group N≤G, [G:N] = 2, then N is a normal subgroup of G
G/N =
G/N = {Ng | g in G} = {gbar| g in G}
If G/ Z(G) is cyclic, then
If G/ Z(G) is cyclic, then G is abelian
H is a normal subgroup of G <=>
H/N is a normal subgroup of G/N
homomorphism
(g1g2)θ = (g1θ)(g2θ)
|G/N| =
[G:N] = |G|/|N|
First isomorphism theorem
G/ker(theta) is isomorphic to Gtheta