đk : x khác 2
\(\left(x-2\right)^2=81\Leftrightarrow\left[{}\begin{matrix}x-2=9\\x-2=-9\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=11\\x=-7\end{matrix}\right.\)
\(ĐK:x\ne2\)
\(\dfrac{2-x}{-27}=\dfrac{-3}{2-x}\)
\(\Leftrightarrow\dfrac{\left(2-x\right)\left(2-x\right)}{-27\left(2-x\right)}=\dfrac{-3.-27}{-27\left(2-x\right)}\)
\(\Leftrightarrow\left(2-x\right)^2=81\)
\(\Leftrightarrow\left(2-x\right)=9^2\)
\(\Leftrightarrow\left[{}\begin{matrix}2-x=9\\2-x=-9\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=-7\\x=11\end{matrix}\right.\)
\(\dfrac{2-x}{-27}=\dfrac{-3}{2-x}\)
\(\dfrac{\left(2-x\right).\left(2-x\right)}{-27.\left(2-x\right)}\)=\(\dfrac{-3.27}{\left(2-x\right).27}\)
\(\dfrac{\left(2-x\right)^2}{-27.\left(2-x\right)}\)=\(\dfrac{-81}{\left(2-x\right).-27}\)
khử mẫu:(2-x)2=-81
2-x=9
2-x=-9