- #1

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## Homework Statement

G={c+di e C| cd =0 and c+d does not =0} a*b=ab

## Homework Equations

OK, I know I need to prove closed under *, and associativity and identity and inverse. I was able to do it for other set, but I do not understand what this set is saying

## The Attempt at a Solution

OK 1, a=c+di and b=e+fi then a*b = (c+di)(e+fi) =ce-de+edi+cfi = ce-de+(ed+cf)i which is in G so yes

Is that correct?