
Andy C. answered 07/27/17
Tutor
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Math/Physics Tutor
Traditional , old school set theory.
let x be an element of N and
n = sup(N), by Zorn's Lemma, which states there
must be a greatest element or upper bound.
Then x<=n because X <=n for all X in N.
Then x is also an element of M=N + mR, as
M = N U mR. So x must be in the union.
So if x is in N, then x is in M.
Hence N is a subset of M.
But n = sup(N) which is also in M
since N is a subset of M.
Since x<=n contained in N contained in M,
x is inside a subset of M.
n = sup(N), by Zorn's Lemma, which states there
must be a greatest element or upper bound.
Then x<=n because X <=n for all X in N.
Then x is also an element of M=N + mR, as
M = N U mR. So x must be in the union.
So if x is in N, then x is in M.
Hence N is a subset of M.
But n = sup(N) which is also in M
since N is a subset of M.
Since x<=n contained in N contained in M,
x is inside a subset of M.