Đề bài

Tính:

a) $\left( {\dfrac{{1 - x}}{x} + {x^2} - 1} \right):\dfrac{{x - 1}}{x}$       

b) $\left( {\dfrac{1}{{{x^2}}} - \dfrac{1}{x}} \right) \cdot \dfrac{{{x^2}}}{y} + \dfrac{x}{y}$                

c) $\dfrac{3}{x} - \dfrac{2}{x}:\dfrac{1}{x} + \dfrac{1}{x} \cdot \dfrac{{{x^2}}}{3}$