b: \(\left(x-\dfrac{2}{9}\right)^3=\left(\dfrac{y}{3}\right)^2=\left(\dfrac{2}{3}\right)^6\)
\(\Leftrightarrow\left\{{}\begin{matrix}\left(x-\dfrac{2}{9}\right)^3=\left(\dfrac{4}{9}\right)^3\\\left(\dfrac{y}{3}\right)^2=\left(\dfrac{8}{27}\right)^2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x-\dfrac{2}{9}=\dfrac{4}{9}\\\dfrac{y}{3}=\dfrac{8}{27}\end{matrix}\right.\\\left\{{}\begin{matrix}x-\dfrac{2}{9}=\dfrac{4}{9}\\\dfrac{y}{3}=-\dfrac{8}{27}\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x=\dfrac{2}{3}\\y=\dfrac{8}{9}\end{matrix}\right.\\\left\{{}\begin{matrix}x=\dfrac{2}{3}\\y=-\dfrac{8}{9}\end{matrix}\right.\end{matrix}\right.\)
c: =>8x-1=5
=>8x=6
hay x=3/4
