As already mentioned by another poster, algebraic numbers are more general than algebraic integers, because the leading coefficient of the polynomial does not have to be one, similarly to the difference between rational numbers and integer numbers, where for the former the denominator does not have to be one, like for the latter.
Ahh, that would explain why the intersection of algebraic integers and Q is Z. I wasn’t convinced of that when I had the notion of algebraic numbers in place of algebraic integers.
I like teaching this kind of stuff to my grade 9 and 10 advanced math classes. It’s not that hard to understand and yet it gives students a sense of wonder about how math works. I might try to show the grade 10s algebraic integers now.
