Ответ:

  1. \(\sqrt{4\cdot25}=\sqrt4\cdot\sqrt{25}=2\cdot5=10\).
  2. \(\sqrt{9\cdot16}=\sqrt9\cdot\sqrt{16}=3\cdot4=12\).
  3. \(\sqrt[3]{8\cdot27}=\sqrt[3]{8}\cdot\sqrt[3]{27}=2\cdot3=6\).
  4. \(\sqrt[4]{16\cdot81}=\sqrt[4]{16}\cdot\sqrt[4]{81}=2\cdot3=6\).
  5. \(\sqrt{\frac{144}{9}}=\frac{\sqrt{144}}{\sqrt9}=\frac{12}{3}=4\).
  6. \(\sqrt[3]{\frac{216}{8}}=\frac{\sqrt[3]{216}}{\sqrt[3]{8}}=\frac{6}{2}=3\).
  7. \(\sqrt[4]{\frac{81}{16}}=\frac{\sqrt[4]{81}}{\sqrt[4]{16}}=\frac{3}{2}\).
  8. \(\sqrt{\sqrt{256}}=\sqrt{16}=4\).