5bквадрат-14ab/25bквадрат -196a квадрат a=-√2 b=√8

Решите задачу:

$\frac{5b^{2}-14ab}{25b^{2}-196a^{2}} = \frac{b(5b-14a)}{(5b-14a)(5b+14a)} =\frac{b}{5b+14a} \\ a=- \sqrt{2} \\ b= \sqrt{8} \\ \frac{\sqrt{8}}{5\sqrt{8}+14*(-\sqrt{2})} =\frac{\sqrt{8}}{\sqrt{25*8}-\sqrt{196*2}} =\frac{\sqrt{8}}{\sqrt{25*8}-\sqrt{392}} =\frac{\sqrt{8}}{\sqrt{25*8}-\sqrt{49*8}} = \\ =\frac{\sqrt{8}}{ \sqrt{8}( \sqrt{25}-\sqrt{49})} =\frac{1}{\sqrt{25}-\sqrt{49}} = \frac{1}{5-7} =- \frac{1}{2}=-0.5$