$$U_{748}(x, y) = \frac{x^{2} \left(1 - \sqrt{1 - 4 y}\right)^{3}}{8 y^{3}} + \frac{x \left(1 - \sqrt{1 - 4 y}\right)^{2}}{2 y^{2}} + \frac{1 - \sqrt{1 - 4 y}}{2 y}$$

$$T_{748}(n, m, k) = \frac{\left(k + n\right) {\binom{2 k}{n}} {\binom{k + 2 m + n - 1}{m}}}{k + m + n}$$