Đặt \(\sqrt[5]{5x+1}=t\Rightarrow x=\frac{t^5-1}{5}\)
\(\lim\limits_{t\rightarrow1}\frac{t-1}{\frac{t^5-1}{5}}=\lim\limits_{t\rightarrow1}\frac{5\left(t-1\right)}{\left(t-1\right)\left(t^4+t^3+t^2+t+1\right)}=\lim\limits_{t\rightarrow1}\frac{5}{t^4+t^3+t^2+t+1}=1\)