\(\lim\limits_{x\rightarrow-\infty}\dfrac{\sqrt{x^2-2x+4}-x}{3x-1}\)
\(=\lim\limits_{x\rightarrow-\infty}\dfrac{-x\cdot\sqrt{1-\dfrac{2}{x}+\dfrac{4}{x^2}}-x}{x\left(3-\dfrac{1}{x}\right)}\)
\(=\lim\limits_{x\rightarrow-\infty}\dfrac{-\sqrt{1-\dfrac{2}{x}+\dfrac{4}{x^2}}-1}{3-\dfrac{1}{x}}\)
\(=\dfrac{-\sqrt{1-0+0}-1}{3}=\dfrac{-2}{3}\)