Ответ:

  1. \(\sqrt4=2\).
  2. \(\sqrt{81}=9\).
  3. \(\sqrt{256}=16\).
  4. \(\sqrt{10000}=100\).
  5. \(\sqrt{27}=3\sqrt3\).
  6. \(\sqrt{18}=3\sqrt2\).
  7. \(\sqrt{0.25}=0.5\).
  8. \(\sqrt5\cdot\sqrt5=5\).
  9. \(\sqrt{18}\cdot\sqrt2=\sqrt{36}=6\).
  10. \(\sqrt{3.6}=\sqrt{36/10}=3\sqrt{10}/5\).
  11. \((\sqrt2)^2=2\).
  12. \((3\sqrt{10})^2=9\cdot10=90\).
  13. \(\sqrt{360}=6\sqrt{10}\).
  14. \(\sqrt{100-36}=\sqrt{64}=8\).
  15. \(\sqrt{100\cdot36}=\sqrt{3600}=60\).
  16. \(\sqrt{15^2+8^2}=\sqrt{225+64}=\sqrt{289}=17\).
  17. \((\sqrt2)^3=2\sqrt2\).
  18. \(7/\sqrt7=\sqrt7\).
  19. По формуле разности квадратов: \((2+\sqrt5)(2-\sqrt5)=4-5=-1\).
  20. \((2-\sqrt5)^2=4-4\sqrt5+5=9-4\sqrt5\).