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**Janu42** OK Thanks.

One more: How do I show the special linear group is normal to the general linear group?

And how do I show that if H is the subgroup of G with 2 x2 matrices where c = 0 (ad does not equal 0), then H is not a normal subgroup of G? I'm assuming if I know how to do the first one I can get this.

EDIT: I saw something about using the special linear group as a kernel or something, but I don't think we know that yet. So if there's a way to use the basic definition of normal subgroups for this, that works.