# Math Help - subring of PID

1. ## subring of PID

I need help with my homework! Can somebody help me please?
I have to show that the subring of principal ideal ring need not to be a principal ideal ring. How can I do it? Thank you very much.

2. Originally Posted by sidi

I need help with my homework! Can somebody help me please?

I have to show that the subring of principal ideal ring need not to be a principal ideal ring. How can I do it? Thank you very much.
there are millions of examples. here's one: $\mathbb{Z}[x]$ is not a PID but $\mathbb{Q}[x]$ obviously is a PID.

3. Thanks