Ответ:
\(\sqrt{\frac{81\cdot25}{16}}=\frac{\sqrt{81}\cdot\sqrt{25}}{\sqrt{16}}=\frac{9\cdot5}{4}=\frac{45}{4}\).
\(\sqrt{\frac{36}{49\cdot121}}=\frac{\sqrt{36}}{\sqrt{49}\cdot\sqrt{121}}=\frac{6}{7\cdot11}=\frac{6}{77}\).
\(\sqrt{\frac{9\cdot16}{25\cdot49}}=\frac{\sqrt9\cdot\sqrt{16}}{\sqrt{25}\cdot\sqrt{49}}=\frac{3\cdot4}{5\cdot7}=\frac{12}{35}\).
