Đáp án: -1/2
Giải thích các bước giải:
$\begin{array}{l}
\mathop {\lim }\limits_{x \to 1} \left( {\frac{2}{{{x^2} - 1}} - \frac{1}{{x - 1}}} \right)\\
= \mathop {\lim }\limits_{x \to 1} \left( {\frac{2}{{\left( {x - 1} \right)\left( {x + 1} \right)}} - \frac{1}{{x - 1}}} \right)\\
= \mathop {\lim }\limits_{x \to 1} \frac{{2 - x - 1}}{{\left( {x - 1} \right)\left( {x + 1} \right)}}\\
= \mathop {\lim }\limits_{x \to 1} \frac{{1 - x}}{{\left( {x - 1} \right)\left( {x + 1} \right)}}\\
= \mathop {\lim }\limits_{x \to 1} \frac{{ - 1}}{{x + 1}}\\
= \frac{{ - 1}}{{1 + 1}} = - \frac{1}{2}
\end{array}$
