$$y^2 - \frac{9y}{7} - 2 = 0$$
$$7y^2 - 9y - 14 = 0$$
Найдем дискриминант:
$$D = (-9)^2 - 4 \cdot 7 \cdot (-14) = 81 + 392 = 473$$
$$y_1 = \frac{-(-9) + \sqrt{473}}{2 \cdot 7} = \frac{9 + \sqrt{473}}{14}$$
$$y_2 = \frac{-(-9) - \sqrt{473}}{2 \cdot 7} = \frac{9 - \sqrt{473}}{14}$$
Ответ: $$y_1 = \frac{9 + \sqrt{473}}{14}$$, $$y_2 = \frac{9 - \sqrt{473}}{14}$$.