Lời giải:
\(\lim\limits_{x\to-\infty}\frac{6x+5}{3x-\sqrt{4x^2+3x+1}}=\lim\limits_{x\to-\infty}\frac{6+\frac{5}{x}}{3+\frac{\sqrt{4x^2+3x+1}}{\left(-x\right)}}\)
\(=\lim\limits_{x\to-\infty}\frac{6+\frac{5}{x}}{3+\sqrt{4-\frac{3}{x}+\frac{1}{x^2}}}=\frac{6}{3+2}=\frac{6}{5}\)