# I Quotienting out by M

#### Mr Davis 97

If $N \trianglelefteq H$, $N \trianglelefteq G$, and $H \le G$, then is it true that $H/N \le G/N$?

I want to use the result for a proof I am currently doing, but I am not sure it is true.
Is it enough just to note that if $h_1,h_2\in H$, then $(h_1N)(h_2^{-1}N) = h_2h_2^{-1}N \in H/N$?

Related Linear and Abstract Algebra News on Phys.org

#### fresh_42

Mentor
2018 Award
If $N \trianglelefteq H$, $N \trianglelefteq G$, and $H \le G$, then is it true that $H/N \le G/N$?

I want to use the result for a proof I am currently doing, but I am not sure it is true.
Is it enough just to note that if $h_1,h_2\in H$, then $(h_1N)(h_2^{-1}N) = h_2h_2^{-1}N \in H/N$?
No, it's wrong. The index before last has to be $1$ The rest is a yes.
E.g.: https://en.wikipedia.org/wiki/Isomorphism_theorems#Third_isomorphism_theorem

• Mr Davis 97

### Want to reply to this thread?

"Quotienting out by M"

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving