# Can we deduce that two rings R1 and R2 are isomorphic if their polynomial ring is iso.?

I will state it again. Given two rings R_1 and R_2 (with or without identity. It's not specified.). If R_1[x] is isomorphic to R_2[y] (No such requirement that the isomorphism sends the constant terms to constant terms), can we deduce that R_1 iso. to R_2?

I feel there might be a counterexample but it's quite hard to find one.

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This is the cancellation problem of Zariski. There are many counterexamples. See math.lsa.umich.edu/~hochster/Lip.text.pdf –  J.C. Ottem Dec 8 '10 at 14:19
This (interesting) question has received many good answers on math.SE: math.stackexchange.com/questions/13504/…. I have voted to close it here as "no longer relevant". –  Pete L. Clark Dec 9 '10 at 1:20