Bezout Identity: Is r∈S U {0} Necessary to Prove?

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The discussion centers on the necessity of demonstrating that r belongs to the set S U {0} in the proof of Bézout's Identity. Participants assert that if r is not in S U {0}, the minimality of d does not apply, preventing the conclusion that r equals zero. The argument emphasizes that for comparisons to be valid, both elements must belong to the same set, specifically S U {0} in this case. Thus, establishing r's membership in S U {0} is crucial for the proof's integrity.

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Suyogya said:
what is the need to show that r belongs to S U {0} in proof (https://en.wikipedia.org/wiki/Bézout's_identity#Proof)

r is zero afterall, whether it lies in S U {0} or not doesn't affect.
If ##r \notin S\cup \{\,0\,\}##, then the minimality of ##d## has nothing to do with ##r## and we cannot conclude ##r=0##. It is zero, because it is part of this set!
 
fresh_42 said:
If ##r \notin S\cup \{\,0\,\}##, then the minimality of ##d## has nothing to do with ##r## and we cannot conclude ##r=0##. It is zero, because it is part of this set!
please tell the following:
is the need to show that r lies in S U {0} just because to compare r is less than or equal to d (as d also belongs to S U {0})?
So are only the same set elements can be compared? If yes, then consider a counter example, set a={10}, set b={5} couldn't we say 5<10 (as both belongs to different sets).
 
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Suyogya said:
please tell the following:
is the need to show that r lies in S U {0} just because to compare r is less than or equal to d (as d also belongs to S U {0})?
So are only the same set elements can be compared? If yes, then consider a counter example, set a={10}, set b={5} couldn't we say 5<10 (as both belongs to different sets).
We start with a set ##M##. Then we choose a minimal element of ##M##, called ##m##. In order to compare any other element ##n## to ##m##, we can only do this, if ##n \in M##, because then we know, that ##m \leq n## as ##m## was chosen minimal. Otherwise we can't say anything.

If in our example, ##d \in S## is minimal, and ##r if \in S \cup \{\,0\,\}##, then either ##r=0## or ##d \leq r##. As ##r < d##, the second is impossible, leaving ##r=0## as only possibility. This entire argument needs ##r if \in S \cup \{\,0\,\}## and that ##d\in S## is the smallest integer there.
 

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