x\(^2\)-7x+6=0
\(\Leftrightarrow\)x\(^2\)-x-6x+6=0
\(\Leftrightarrow\)x(x-1)-6(x-1)=0
\(\Leftrightarrow\)(x-1)(x-6)=0
\(\Leftrightarrow\)\(\left[{}\begin{matrix}x-1=0\\x-6=0\end{matrix}\right.\)
\(\Leftrightarrow\)\(\left[{}\begin{matrix}x=1\\x=6\end{matrix}\right.\)
Vậy S={1;6}