Номер 8 и 9 срочноооо

8.
$\dfrac{x-y}{x^2y-xy^2-y^3} : \dfrac{1}{x^2-xy-y^2} = \dfrac{x-y}{y(x^2-xy-y^2)} \cdot (x^2-xy-y^2)= \\\ = \dfrac{(x-y)(x^2-xy-y^2)}{y(x^2-xy-y^2)} = \dfrac{x-y}{y} =\dfrac{8m}{m} =8$

9.
$f\left(- \dfrac{2}{5} k\right)+f\left(-5k\right)= \dfrac{k}{\left|- \dfrac{2}{5} k\right|} + \dfrac{k}{|-5k|} = \\\ = \dfrac{k}{ \dfrac{2}{5} k} + \dfrac{k}{5k} = \dfrac{5}{2} + \dfrac{1}{5} = 2.5+0.2=2.7$