2. (a) Let de Z\ {0, 1} be square-free. Let a € Z[√] \ {0} and assume that N(a) is a prime number. Show that a is an irreducible element of Z[√]. (b) Hence find an irreducible element of Z[2] which is not real.

Find all monic irreducible polynomials of degree 2 over Z3.

Prove that every ordered integral domain has characteristic zero.

For an element x of an ordered integral domain D, the absolute value | x | is defined by | x |={ xifx0xif0x Prove that | x |=| x | for all xD. Prove that | x |x| x | for all xD. Prove that | xy |=| x || y | for all x,yD. Prove that | x+y || x |+| y | for all x,yD. Prove that | | x || y | || xy | for all x,yD.