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

$\mathop {\lim }\limits_{x \to  - \infty } {{\left( {2x - 1} \right)\sqrt {{x^2} - 3} } \over {x - 5{x^2}}}$  

$\mathop {\lim }\limits_{x \to  + \infty } \sqrt {{{{x^4} +{x^2} + 2} \over {\left( {{x^3} + 1} \right)\left( {3x - 1} \right)}}}$       

$\mathop {\lim }\limits_{x \to  - \infty } {{2x - 3} \over {\sqrt {{x^2} + 1}  - x}}.$