Proving Ring Isomorphism of Q[x]/<x^2-2> and Q[sqrt2]

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SUMMARY

The discussion focuses on proving the ring isomorphism between Q[x]/ and Q[sqrt2]. The key is to define the function f(a+bx) = a + b(sqrt2), which establishes the isomorphism by demonstrating that elements in Q[x]/(x^2-2) can be expressed in the form a + bx. Participants confirm that showing x^2 - 2 is in the kernel is unnecessary for this proof, as the isomorphism is evident from the structure of the rings involved.

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  • Understanding of ring theory and isomorphisms
  • Familiarity with polynomial rings, specifically Q[x]
  • Knowledge of field extensions, particularly Q[sqrt2]
  • Basic concepts of kernels in ring homomorphisms
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what is the easiest way to show that
Q[x]/<x^2-2> is ring isomorphic to
Q[sqrt2]={a+b(sqrt2)|a,b in Q}

just give me a hint how to start
 
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anyone?

do I have to show that x^2 - 2 is in the kernal?
 
why don't you just write down the (obvious) isomorphism? (obvious in the sense of one side only has x as a special quantity, the other sqrt(2), and anything in Q[x]/(x^2-2) is of the form a+bx, isn't it...)
 
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yes! thank you. the example in the book goes into too much detail and I was trying follow that, but yes the function f(a+bx)=a+b(sqrt2) is a ring isomorphism.
 

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