1) √0,81 · √36; 2) √(64/9); 3) √(21/49). Вычислить.

1. \(\sqrt{0.81}\cdot\sqrt{36}=0.9\cdot6=5.4\).
2. \(\sqrt{\frac{64}{9}}=\frac{\sqrt{64}}{\sqrt{9}}=\frac{8}{3}\).
3. \(\sqrt{\frac{21}{49}}=\frac{\sqrt{21}}{7}\).

Ответ: 1) 5.4; 2) \(\frac{8}{3}\); 3) \(\frac{\sqrt{21}}{7}\).