б) c/√c-10 - 20√c-100/√c-10

б) $$\frac{c}{\sqrt{c} - 10} - \frac{20\sqrt{c} - 100}{\sqrt{c} - 10} = \frac{c - 20\sqrt{c} + 100}{\sqrt{c} - 10} = \frac{(\sqrt{c} - 10)^2}{\sqrt{c} - 10} = \sqrt{c} - 10$$.

Ответ: $$\sqrt{c} - 10$$