\(x^2-2x-1=0\)
\(\Leftrightarrow x^2-2x+1-2=0\)
\(\Leftrightarrow\left(x-1\right)^2=2\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=\sqrt{2}\\x-1=-\sqrt{2}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1+\sqrt{2}\\x=1-\sqrt{2}\end{matrix}\right.\)
vậy--