because it's not a domain: suppose there's a ring monomorphism where F is a field. we have f(2)f(3) = f(6) = f(0) = 0. but F is a domain and thus either f(2) = 0 or f(3) = 0.

since f is one-to-one, we get either 2 = 0 or 3 = 0 in which is nonsense.

let Q be the quotient field of a field D. define the map \to Q" alt="g \to Q" /> by show that g is a ring isomorphism.The field of quotients of any field D is isomorphic to D. Why?