Question: is 2z/8z isomorphic to z4?
Answer: 7. Prove that 2Z/8Z is not isomorphic to Z4 as rings. [2] ANSWER: Claim Z4 has a unity but 2Z/8Z does not. ANSWER: If x + J has an inverse f(x) + J, then xf(x) + J = (x + J)(f(x) + J)=1+ J.