(f, g, K)
Compute multiplicative inverse of `f` modulo `g` in `F[x]`.

    Examples
    ========

    >>> from sympy.polys import ring, QQ
    >>> R, x = ring("x", QQ)

    >>> f = x**2 - 1
    >>> g = 2*x - 1
    >>> h = x - 1

    >>> R.dup_invert(f, g)
    -4/3

    >>> R.dup_invert(f, h)
    Traceback (most recent call last):
    ...
    NotInvertible: zero divisor
Compute multiplicative inverse of `f` modulo `g` in `F[x]`.
Compute multiplicative inverse of f modulo g in F [ x ] .
def dup_invert(f, g, K):
    """
    Compute multiplicative inverse of `f` modulo `g` in `F[x]`.

    Examples
    ========

    >>> from sympy.polys import ring, QQ
    >>> R, x = ring("x", QQ)

    >>> f = x**2 - 1
    >>> g = 2*x - 1
    >>> h = x - 1

    >>> R.dup_invert(f, g)
    -4/3

    >>> R.dup_invert(f, h)
    Traceback (most recent call last):
    ...
    NotInvertible: zero divisor

    """
    s, h = dup_half_gcdex(f, g, K)

    if h == [K.one]:
        return dup_rem(s, g, K)
    else:
        raise NotInvertible("zero divisor")
def dup_invert ( f , g , K ) : s , h = dup_half_gcdex ( f , g , K ) if h == [ K . one ] : return dup_rem ( s , g , K ) else : raise NotInvertible ( "zero divisor" )