Tính các giới hạn sau: lim x suy ra - vô cùng ((9x^2 + 3) / (x + 1))
Tính các giới hạn sau:
\(\mathop {\lim }\limits_{x \to - \infty } \frac{{\sqrt {9{x^2} + 3} }}{{x + 1}}\);
\(\mathop {\lim }\limits_{x \to - \infty } \frac{{\sqrt {9{x^2} + 3} }}{{x + 1}}\) \( = \mathop {\lim }\limits_{x \to - \infty } \frac{{\sqrt {{x^2}\left( {9 + \frac{3}{{{x^2}}}} \right)} }}{{x + 1}}\)\( = \mathop {\lim }\limits_{x \to - \infty } \frac{{\left| x \right|.\sqrt {9 + \frac{3}{{{x^2}}}} }}{{x + 1}}\)
\( = \mathop {\lim }\limits_{x \to - \infty } \frac{{\left( { - x} \right).\sqrt {9 + \frac{3}{{{x^2}}}} }}{{x\left( {1 + \frac{1}{x}} \right)}} = \mathop {\lim }\limits_{x \to - \infty } \frac{{ - \sqrt {9 + \frac{3}{{{x^2}}}} }}{{1 + \frac{1}{x}}} = \frac{{ - \sqrt 9 }}{1} = - 3\).