Ответ:

В разложении \((u+v)^n\) четвёртый член равен \(\binom{n}{3}u^{n-3}v^3\).

  1. \(\binom{12}{3}(\sqrt{x})^9x^3=220x^{15/2}\).
  2. \(\binom{14}{3}x^{11}(-\sqrt{x})^3=-364x^{25/2}\).
  3. \(\binom{13}{3}x^{10}(-1/x)^3=-286x^7\).
  4. \(\binom{11}{3}(1/x)^8x^3=165x^{-5}\).
  5. \(\binom{9}{3}(a^{0.1})^6(a^{0.2})^3=84a^{1.2}\).
  6. \(\binom{8}{3}(b^{0.3})^5(b^{0.4})^3=56b^{2.7}\).