Câu hỏi :

Kết quả \(\mathop {\lim }\limits_{x \to - 1} \frac{{x + 1}}{{2{x^3} + 2}}\) bằng:

A. \(0\).

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

C. \(\frac{1}{6}\).

D. \(\frac{1}{2}\).

* Đáp án

* Hướng dẫn giải

Ta có:

\(\mathop {\lim }\limits_{x \to - 1} \frac{{x + 1}}{{2{x^3} + 2}} = \mathop {\lim }\limits_{x \to - 1} \frac{{x + 1}}{{2\left( {{x^3} + 1} \right)}} = \mathop {\lim }\limits_{x \to - 1} \frac{{x + 1}}{{2\left( {x + 1} \right)\left( {{x^2} - x + 1} \right)}} = \mathop {\lim }\limits_{x \to - 1} \frac{1}{{2\left( {{x^2} - x + 1} \right)}} = \frac{1}{{2.3}} = \frac{1}{6}.\)

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