[tex]\it a)\ \dfrac{x-4}{2x-8}= \dfrac{x-4}{2(x-4)}= \dfrac{1}{2}\\ \\ \\ b)\ \ \dfrac{xy-x}{y^2-y}= \dfrac{x(y-1)}{y(y-1)}= \dfrac{x}{y}\\ \\ \\ c)\ \ \dfrac{a^2-b^2}{ax-xb}= \dfrac{(a-b)(a+b)}{x(a-b)}= \dfrac{a+b}{x}[/tex]
