346 1) (√8 + √2)²; 2) (√7 - √28)²; 3) (√7 + √6)(√7 - √6); 4) (5√2 + 2√5)(5√2 - 2√5).

346

1. $$(\sqrt{8} + \sqrt{2})^2 = (\sqrt{8})^2 + 2 \cdot \sqrt{8} \cdot \sqrt{2} + (\sqrt{2})^2 = 8 + 2 \cdot \sqrt{16} + 2 = 10 + 2 \cdot 4 = 10 + 8 = 18$$

   Ответ: 18

2. $$(\sqrt{7} - \sqrt{28})^2 = (\sqrt{7} - \sqrt{4 \cdot 7})^2 = (\sqrt{7} - 2\sqrt{7})^2 = (-\sqrt{7})^2 = 7$$

   Ответ: 7

3. $$(\sqrt{7} + \sqrt{6})(\sqrt{7} - \sqrt{6}) = (\sqrt{7})^2 - (\sqrt{6})^2 = 7 - 6 = 1$$

   Ответ: 1

4. $$(5\sqrt{2} + 2\sqrt{5})(5\sqrt{2} - 2\sqrt{5}) = (5\sqrt{2})^2 - (2\sqrt{5})^2 = 25 \cdot 2 - 4 \cdot 5 = 50 - 20 = 30$$

   Ответ: 30