3. Сократи дробь (√14 - √28) / √7

$$\frac{\sqrt{14} - \sqrt{28}}{\sqrt{7}} = \frac{\sqrt{14} - \sqrt{4 \cdot 7}}{\sqrt{7}} = \frac{\sqrt{14} - 2\sqrt{7}}{\sqrt{7}} = \frac{\sqrt{2 \cdot 7} - 2\sqrt{7}}{\sqrt{7}} = \frac{\sqrt{7}(\sqrt{2} - 2)}{\sqrt{7}} = \sqrt{2} - 2$$

Ответ: $$ \sqrt{2} - 2$$