ta có : \(\dfrac{lim}{x\rightarrow-\infty}\left(2x-1\right)\sqrt{\dfrac{x-1}{4x^2+x-5}}=\dfrac{lim}{x\rightarrow-\infty}\left(2x-1\right)\sqrt{\dfrac{x-1}{\left(x-1\right)\left(4x+5\right)}}\)
\(=\dfrac{lim}{x\rightarrow-\infty}\left(2x-1\right)\sqrt{\dfrac{1}{4x+5}}\) cái này không xác định .