(2,5x - 4/3)2 - 5/6 = -7/18
=> (2,5x - 4/3)2 = -7/18 + 5/6
=> (2,5x - 4/3)2 = 4/9
=> (2,5x - 4/3)2 = (2/3)2
=> \(\orbr{\begin{cases}2,5x-\frac{4}{3}=\frac{2}{3}\\2,5x-\frac{4}{3}=-\frac{2}{3}\end{cases}}\)
=> \(\orbr{\begin{cases}x=\frac{4}{5}\\x=\frac{4}{15}\end{cases}}\)
\(\left(2,5x-\frac{4}{3}\right)^2-\frac{5}{6}=-\frac{7}{18}\)
\(\left(2,5x-\frac{4}{3}\right)^2=-\frac{7}{18}+\frac{5}{6}\)
\(\left(2,5x-\frac{4}{3}\right)^2=\frac{4}{9}\)
\(\Rightarrow\orbr{\begin{cases}x=\frac{4}{5}\\x=\frac{4}{15}\end{cases}}\)