Ответ:

  1. \(\dfrac{-a^2}{a^3}=-\dfrac{1}{a}\).
  2. \(\dfrac{8x^7y(a+b)}{22x^{13}y^3(a+b)}=\dfrac{4}{11x^6y^2}\).
  3. \(\dfrac{2a(b+c)}{4a^3(b+c)(b-c)}=\dfrac{1}{2a^2(b-c)}\).
  4. Так как \(y-x=-(x-y)\), то \(\dfrac{6(x-y)}{12z(y-x)}=-\dfrac{1}{2z}\).
  5. \(\dfrac{(x+8)^5}{(x+8)^2}=(x+8)^3\).

Ответ: \(-\dfrac1a;\ \dfrac{4}{11x^6y^2};\ \dfrac{1}{2a^2(b-c)};\ -\dfrac1{2z};\ (x+8)^3\).