  We find all spectral type differential equations satisfied by the symmetric
generalized ultraspherical polynomials which are orthogonal on the interval
[-1,1] with respect to the classical symmetric weight function for the Jacobi
polynomials together with equal mass points at both ends of the interval of
orthogonality.
  In order to find explicit formulas for the coefficients of these differential
equations we have to solve systems of equations involving derivatives of the
classical Jacobi polynomials. These systems of equations have a unique solution
which is given explicitly. This is a consequence of the Jacobi inversion
formula.
