I am reading this in my text and I'm confused about why matrices and polynomials can be treated as vectors?

[![enter image description here](https://i.stack.imgur.com/WWuX0.png)](https://i.stack.imgur.com/WWuX0.png)

Previously, there was an example that looked like this:

[![enter image description here](https://i.stack.imgur.com/sfPZ4.png)](https://i.stack.imgur.com/sfPZ4.png)

So I guess that vectors can be both polynomials and matrices?

My previous reading about vectors is this:

[![enter image description here](https://i.stack.imgur.com/Vp1zk.png)](https://i.stack.imgur.com/Vp1zk.png)

I guess the main idea is that polynomials and matrices are vector spaces which I read about here:

[![enter image description here](https://i.stack.imgur.com/WXwcy.png)](https://i.stack.imgur.com/WXwcy.png)