Let R be a commutative ring. Let A0 be an ideal in R[x] such that
the lowest degree of a nonzero polynomial in A is n1 and such that A
contains a monic polynomial of degree n. Prove that A is a principal ideal
in R[x].

letbe a monic polynomial of degree
obviously
now using induction over degrees of elements of
we show that every elment of
is divisible by
which will
prove thatso let
then
is a polynomial of degree at most
and thus by the minimality of
we have
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thusthis proves the base of the induction. now let
and suppose every polynomial in
of degree at most
is in
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letthen
and
thus by induction hypothesis
for some
then
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