a: \(\dfrac{2}{5}-x=\dfrac{6}{5}\)
=>\(x=\dfrac{2}{5}-\dfrac{6}{5}\)
=>\(x=\dfrac{2-6}{5}=-\dfrac{4}{5}\)
b: \(\dfrac{4}{5}-\left|x-\dfrac{2}{3}\right|=\dfrac{2}{3}\)
=>\(\left|x-\dfrac{2}{3}\right|=\dfrac{4}{5}-\dfrac{2}{3}=\dfrac{12-10}{15}=\dfrac{2}{15}\)
=>\(\left[{}\begin{matrix}x-\dfrac{2}{3}=\dfrac{2}{15}\\x-\dfrac{2}{3}=-\dfrac{2}{15}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}+\dfrac{2}{15}=\dfrac{12}{15}=\dfrac{4}{5}\\x=\dfrac{2}{3}-\dfrac{2}{15}=\dfrac{10}{15}-\dfrac{2}{15}=\dfrac{8}{15}\end{matrix}\right.\)
c: \(\dfrac{x-1}{3}=\dfrac{27}{x-1}\)
=>\(\left(x-1\right)^2=3\cdot27=81\)
=>\(\left[{}\begin{matrix}x-1=9\\x-1=-9\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=10\left(nhận\right)\\x=-8\left(nhận\right)\end{matrix}\right.\)
