Đáp án:
$\lim_{x \to x_o}\dfrac{\dfrac{x+1}{x-1}-\dfrac{x_o+1}{x_o-1}}{x-x_o}$
$=\lim_{x \to 0}\dfrac{\dfrac{x+1}{x-1}+1}{x}$
$=\lim_{x \to 0}\dfrac{\dfrac{x+1}{x-1}+\dfrac{x-1}{x-1}}{x}$
$=\lim_{x \to 0}(\dfrac{2x}{x-1}.\dfrac{1}{x})$
$=\lim_{x \to 0}\dfrac{2}{x-1}=\dfrac{2}{0-1}=-2$
BẠN THAM KHẢO.