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My question, how can I use ##x^2 = -1## to show that they are not isomorphic? Using ##x^3 = 1## is more clear because any isomorphism would preserve powers and preserve the identity. But using ##x^2 = -1## is less clear to me.

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- Thread starter Mr Davis 97
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- #1

- 1,456

- 44

My question, how can I use ##x^2 = -1## to show that they are not isomorphic? Using ##x^3 = 1## is more clear because any isomorphism would preserve powers and preserve the identity. But using ##x^2 = -1## is less clear to me.

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fresh_42

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Edit: I think I got it: Consider ##\varphi(-1)\cdot \varphi (-1)##.

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