Đặt \(t=\sqrt[7]{2-x}\rightarrow x=2-t^7.x\rightarrow1\Rightarrow t\rightarrow1\)
\(\Rightarrow lim_{t\rightarrow1}\dfrac{t-1}{-\left(t^7-1\right)}=lim_{x\rightarrow1}\dfrac{t-1}{-\left(t-1\right)\left(t^6+t^5+t^4+t^3+t^2+t+1\right)}\)\(=lim_{t\rightarrow1}\dfrac{-1}{t^6+t^5+t^4+t^3+t^2+t+1}=-\dfrac{1}{7}\)