Đáp án:
Giải thích các bước giải:
\(\begin{array}{l}
\mathop {\lim }\limits_{x \to - \infty } \left( {3x + \sqrt {9{x^2} - 7x + 1} } \right) = \mathop {\lim }\limits_{x \to - \infty } \frac{{9{x^2} - 9{x^2} + 7x - 1}}{{3x - \sqrt {9{x^2} - 7x + 1} }}\\
\mathop {\lim }\limits_{x \to - \infty } \frac{{7x - 1}}{{3x - \sqrt {9{x^2} - 7x + 1} }} = \mathop {\lim }\limits_{x \to - \infty } \frac{{7 - \frac{1}{x}}}{{3 - \left( { - \sqrt {9 - \frac{7}{x} + \frac{1}{{{x^2}}}} } \right)}} = \frac{7}{6}
\end{array}\)
