\(\Leftrightarrow x^2-2x+1-64=0\)
\(\Leftrightarrow\left(x-1\right)^2=64\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=8\\x-1=-8\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=9\\x=-7\end{matrix}\right.\) ( TM )
\(\Delta'=\left(-1\right)^2-1\times\left(-63\right)=1+63=64\)
\(\Rightarrow\) phương trình có 2 nghiệm phân biệt : \(x_1=\frac{-b'+\sqrt{\Delta'}}{a}=\frac{-\left(-1\right)+\sqrt{64}}{1}=9\)
\(x_2=\frac{-b'-\sqrt{\Delta'}}{a}=\frac{-\left(-1\right)-\sqrt{64}}{1}=-7\)
Vậy \(S=\left\{9;-7\right\}\)