Вычислите

1. a) $$\sqrt{0.64 \cdot 36} = \sqrt{0.64} \cdot \sqrt{36} = 0.8 \cdot 6 = 4.8$$.
2. б) $$\sqrt{8} - \sqrt{72} = \sqrt{8} - \sqrt{36 \cdot 2} = \sqrt{8} - \sqrt{36} \cdot \sqrt{2} = \sqrt{8} - 6\sqrt{2} = \sqrt{4 \cdot 2} - 6\sqrt{2} = 2\sqrt{2} - 6\sqrt{2} = -4\sqrt{2}$$.
3. в) $$\sqrt{48} \cdot \sqrt{3} = \sqrt{48 \cdot 3} = \sqrt{144} = 12$$.