1. (E, +} is a group. Clearly E is closed under addition. Also the addition of numbers is associative- The identity},r element is e = CI, since a + l} = U + a. = a. for all a E 3. What about it"? Here too, since e:0=a'+c=a+a', the a' in this instance is a., and clearly a+(e]=(o)+u=. 2. (E, .) and (E', .) are not groups, since inverse do not always exit. 5-\" [Q', +) is not a group (Q is not closed under addition: 1, 1 are both in IQ\" but 1+ (1) = D is not in IQ\") (11*, .), (13\