# Normal subgroup

1. May 16, 2012

### e179285

H=A3= {(1),(1 2 3),(1 3 2)} and

G=S3 ={ (1),(1 2 3),(1 3 2),(1 2 ),(1 3),(1 2 3) }

Is H is normal subgroup of G ?
I try g=(1 2 3 ) for gH=Hg but gH≠Hg for all g ε G.In this situation,H is normal subgroup pf G?

2. May 18, 2012

### Dustinsfl

I haven't check your assertion, but in order for H to be a normal subgroup of G, $gH = Hg$ for all $g\in G$.

If you have $gH\neq Hg$ for some $g\in G$, then H isn't a normal subgroup of G.

3. May 18, 2012

### micromass

What is [G]?? What does that tell you??