1) 2√7 = √4 * √7 = √28 2) 3√11 = √9 * √11 = √99 3) 0,2√5 = √0,04 * √5 = √0,2 4) 1/3√54 = √1/9 * √54 = √54/9 = √6

Решение:

1. \(2\sqrt{7} = \sqrt{2^2} \cdot \sqrt{7} = \sqrt{4 \cdot 7} = \sqrt{28}\)
2. \(3\sqrt{11} = \sqrt{3^2} \cdot \sqrt{11} = \sqrt{9 \cdot 11} = \sqrt{99}\)
3. \(0.2\sqrt{5} = \sqrt{0.2^2} \cdot \sqrt{5} = \sqrt{0.04 \cdot 5} = \sqrt{0.2}\)
4. \(\frac{1}{3}\sqrt{54} = \sqrt{\left(\frac{1}{3}\right)^2} \cdot \sqrt{54} = \sqrt{\frac{1}{9} \cdot 54} = \sqrt{\frac{54}{9}} = \sqrt{6}\)

Ответ: 1) \(\sqrt{28}\), 2) \(\sqrt{99}\), 3) \(\sqrt{0.2}\), 4) \(\sqrt{6}\).