$$U_{897}(x, y) = x \left(1 - y\right)^{2} + \frac{\sqrt{\frac{4 x}{1 - y} + \frac{1}{\left(1 - y\right)^{6}}}}{2} + \frac{1}{2 \left(1 - y\right)^{3}}$$

$$T_{897}(n, m, k) = \begin{cases}{\binom{3 k + m - 1}{m}}&\text{if n=0} ,\ \\\frac{2 \left(-1\right)^{n - 1} k {\binom{- 2 k + 2 n - 1}{n - 1}} {\binom{3 k + m - 5 n - 1}{m}}}{n} \end{cases} $$