\(a,\frac{1-2x}{8}=\frac{-4}{2\left(2x-1\right)}\)
\(\Rightarrow2\left(1-2x\right)\left(2x-1\right)=-32\)
\(\Rightarrow2\left(2x-1\right)\left(2x-1\right)=32\)
\(\Rightarrow\left(2x-1\right)^2=16\)
\(\Rightarrow\orbr{\begin{cases}2x-1=4\\2x-1=-4\end{cases}\Rightarrow\orbr{\begin{cases}2x=5\\2x=-3\end{cases}\Rightarrow}\orbr{\begin{cases}x=\frac{5}{2}\\x=-\frac{3}{2}\end{cases}}}\)
\(b,\frac{-2}{x-1}=\frac{1-x}{\frac{8}{25}}\)
\(\Leftrightarrow(x-1)(1-x)=-\frac{16}{25}\)
\(\Leftrightarrow-(x-1)^2=-\frac{16}{25}\)
\(\Leftrightarrow-(x+1)^2=\left[-\frac{4}{5}\right]^2=\left[\frac{4}{5}\right]^2\)
\(\Leftrightarrow\orbr{\begin{cases}-x+1=-\frac{4}{5}\\-x+1=\frac{4}{5}\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=\frac{9}{5}\\x=\frac{1}{5}\end{cases}}\)
