U_{m} (ξ) \sim D_{m} (ξ) - \frac{1}{2^{6} h} (D_{m + 4} (ξ) - 4! (\binom{m}{4}) D_{m - 4} (ξ)) + \frac{1}{2^{13} h^{2}} (D_{m + 8} (ξ) - 2^{5} (m + 2) D_{m + 4} (ξ) + 4! 2^{5} (m - 1) (\binom{m}{4}) D_{m - 4} (ξ) + 8! \frac{m}{8} D_{m - 8} (ξ)) + \dots