6. Сократите дробь: a) 5-V5 V10-12 б) 6-4 16-2

а) $$\frac{5-\sqrt{5}}{\sqrt{10}-\sqrt{2}} = \frac{\sqrt{5}(\sqrt{5}-1)}{\sqrt{2}(\sqrt{5}-1)} = \frac{\sqrt{5}}{\sqrt{2}} = \frac{\sqrt{5} \cdot \sqrt{2}}{\sqrt{2} \cdot \sqrt{2}} = \frac{\sqrt{10}}{2}$$.

б) $$\frac{b-4}{\sqrt{b}-2} = \frac{(\sqrt{b}-2)(\sqrt{b}+2)}{\sqrt{b}-2} = \sqrt{b}+2$$.

Ответ: a) $$\frac{\sqrt{10}}{2}$$; б) $$\sqrt{b}+2$$.