\(5x^2-25x-4=0\)
\(\Leftrightarrow x^2-5x-\frac{4}{5}=0\)
\(\Leftrightarrow x^2-5x+\frac{25}{4}=\frac{141}{20}\)
\(\Leftrightarrow\left(x-\frac{5}{2}\right)^2=\frac{141}{20}\)
\(\Leftrightarrow\orbr{\begin{cases}x-\frac{5}{2}=\frac{\sqrt{705}}{10}\\x-\frac{5}{2}=-\frac{\sqrt{705}}{10}\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=\frac{25+\sqrt{705}}{10}\\x=\frac{25-\sqrt{705}}{10}\end{cases}}\)