Prove or disprove if D is an integral domain then every prim
Prove or disprove: if D is an integral domain, then every prime element in D is also irreducible in D.
Solution
if D is an integral domain, then every prime element in D is also irreducible in D the statement is false.
let D is a integral domain.
and let a D is prime element
now assume that Assume a = mn in D
so a|mn implies either a|m or a|n as a is prime
let a|m than m = aD
we have a = mn so a = anD hence nD = 1 since we’re in an integral domain and n is a unit.
so in general, irreducibles might not be prime.
or other proof like:
Suppose that D is an integral domain, and suppose p is an element that is reducible as p = ab, with neither a nor b a unit.
Then p divides itself, the product of a and b, but does not divide either a or b
if it divided one, the other must be a unit as multiplicative cancellation holds in an integral domain.
Therefore p cannot be prime.
