(3x-1)^4=81
⇔\(\left[ \begin{array}{l}(3x-1)^4=3^4\\(3x-1)^4=(-3)^4\end{array} \right.\)
⇔\(\left[ \begin{array}{l}3x-1=3\\3x-1=-3\end{array} \right.\)
⇔\(\left[ \begin{array}{l}3x=4\\3x=-2\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=4/3\\x=-2/3\end{array} \right.\)
(Cho mk ctlhn đc hk ạ?)