In: Advanced Math
Show that f(x) = x^4+x^3+3x^2+7x−8 is irreducible over Z.
We note that
is irreducible over
if and
only if it is irreducible over
And
is irreducible over
if and
only if
is irreducible over
That is,
is irreducible over
By Eisenstien's criteion for
and for
we have
(the first terms coefficient),
(the
coefficients of the rest of the terms) and
(coefficient of the constant term)
Therefore,
is not reducible over
Which by the above consideration means
is irreducible over