subring

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Defines:
ideal
Type of Math Object:
Definition
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Reference
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Mathematics Subject Classification

Subring criterion

The subset S of Z[X] which consists of polynomials with positive constant term is closed under addition and multiplication, but S is not subring of Z[X].

The sufficient (and necessary) subring criterion is that the non-empty S is closed under subtraction and multiplication.

Re: Subring criterion

the proper way is not to post a message but to file a correction, no point in doing both
f
G -----> H G
p \ /_ ----- ~ f(G)
\ / f ker f
G/ker f