\(\mathop {\lim }\limits_{x \to + \infty } \frac{{3{x^2} - {x^5}}}{{{x^4} + x + 5}}\)

* Hướng dẫn giải

\(\mathop {\lim }\limits_{x \to  + \infty } \frac{{3{x^2} - {x^5}}}{{{x^4} + x + 5}} = \mathop {\lim }\limits_{x \to  + \infty } \frac{{x\left( {\frac{3}{{{x^3}}} - 1} \right)}}{{1 + \frac{1}{{{x^3}}} + \frac{5}{{{x^4}}}}} =  - \infty \)