For a) the question is now wanting you to find a map from G to another group, H, such that the kernel is the set of all matrices such that . It is analogous for b).

If you have any trouble finding these maps, just ask. People will happily surrender the answers, but you finding them yourself is much, much more useful!

Finally, what are your matrices over? ? ? ? Some arbitrary field? (The question doesn't really make sense unless you know this...)