1. Show that is not isomorphic to .

2. Show that no two of are isomorphic,

3. Show that \ is a group under multiplication. H is quaternion algebra.

My solutions:

1. The set of rational number is commutative, but is not, so would that be the reason?

2. I want to say that T contains element with the order 6 while does not, would that be right?

3. For this one I'm just simply lost, would anyone please explain more what H is?

Thanks.