Ответ:

  1. a/√11 = a√11/11.
  2. 18/√6 = 3√6.
  3. 5/√10 = √10/2.
  4. 13/√26 = √26/2.
  5. 30/√15 = 2√15.
  6. 2/(3√x) = 2√x/(3x), при x > 0.