\[\frac{2}{x^{2} - 5x + 6} + \frac{3}{x^{2} - 5x + 7} =\]
\[= \frac{8}{x^{2} - 5x + 8}\]
\[Пусть\ \ t = x^{2} - 5x + 6:\ \]
\[- 3t^{2} + 4t + 4 = 0\]
\[3t^{2} - 4t - 4 = 0\]
\[D_{1} = 4 + 12 = 16\]
\[t_{1} = \frac{2 + 4}{3} = 2;\ \ \ \]
\[t_{2} = \frac{2 - 4}{3} = - \frac{2}{3}.\]