Giới hạn lim x → a − 1 /(x − a) bằng:

3/22

Giới hạn \(\mathop {\lim }\limits_{x \to {a^ - }} \frac{1}{{x - a}}\) bằng:

\( - \frac{1}{{2a}}\).

\(0\).

\( + \infty \).

\( - \infty \).

Giải thích

Chọn D

Ta có: \(\left\{ {\begin{array}{*{20}{l}}{\mathop {\lim }\limits_{x \to {a^ - }} 1 = 1 > 0}\\{\mathop {\lim }\limits_{x \to {a^ - }} \left( {1 - a} \right) = 0}\\{x - a < 0{\rm{ khi }}x \to {a^ - }}\end{array}} \right.\)

Vậy \(\mathop {\lim }\limits_{x \to {a^ - }} \frac{1}{{x - a}} = - \infty \).