Bài giải
$(3x-1)^{3}$ + 3 = 3 ( x + $\frac{2}{3}$ )
$(3x-1)^{3}$+3= 3x + 2
$(3x-1)^{3}$ = 3x + 2 - 3
$(3x-1)^{3}$ = 3x - 1
$(3x-1)^{2}$=1
⇒\(\left[ \begin{array}{l}3x-1=-1\\3x-1=1\end{array} \right.\) ⇒ \(\left[ \begin{array}{l}3x=0\\3x=2\end{array} \right.\) ⇒ \(\left[ \begin{array}{l}x=0\\x= \frac{2}{3} \end{array} \right.\)
⇒ x ∈ { 0 ; $\frac{x}{y}$ }
