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