(d) Explain why the following "proof" is incorrect: "Claim: The integral domain R = {a+b√√2 | a, b = Z} is not a unique factorisation domain. Proof. In R we have the factorisations 2 = √√2. √2 and 2 (2+√2) (2 - √2). These are two different factorisations of the element 2 Є R, which shows that R is not a unique factorisation domain." (e) Is the element 7+ 5√2 a unit of the integral domain R = {a + b√√2 | a, b = Z}? Justify your answer.

Advanced Engineering Mathematics
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ISBN:9780470458365
Author:Erwin Kreyszig
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Chapter2: Second-order Linear Odes
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(d) Explain why the following "proof" is incorrect:
"Claim: The integral domain R = {a+b√√2 | a, b = Z} is not a unique
factorisation domain.
Proof. In R we have the factorisations 2 = √√2. √2 and
2 (2+√2) (2 - √2). These are two different factorisations of the
element 2 Є R, which shows that R is not a unique factorisation
domain."
(e) Is the element 7+ 5√2 a unit of the integral domain R = {a + b√√2 | a, b = Z}?
Justify your answer.
Transcribed Image Text:(d) Explain why the following "proof" is incorrect: "Claim: The integral domain R = {a+b√√2 | a, b = Z} is not a unique factorisation domain. Proof. In R we have the factorisations 2 = √√2. √2 and 2 (2+√2) (2 - √2). These are two different factorisations of the element 2 Є R, which shows that R is not a unique factorisation domain." (e) Is the element 7+ 5√2 a unit of the integral domain R = {a + b√√2 | a, b = Z}? Justify your answer.
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