def discriminant(x):
    """
    Return the discriminant of ``x``.

    EXAMPLES::

        sage: R.<x> = PolynomialRing(QQ)
        sage: S = R.quotient(x^29 - 17*x - 1, 'alpha')
        sage: K = S.number_field()
        sage: discriminant(K)
        -15975100446626038280218213241591829458737190477345113376757479850566957249523
    """
    return x.discriminant()