\(\sqrt{x^2-8x+16}=7\Leftrightarrow\sqrt{x^2-2.x.4+4^2}=7\Leftrightarrow\sqrt{\left(x-4\right)^2}=7\Leftrightarrow\left|x-4\right|=7\Leftrightarrow\)\(\left[{}\begin{matrix}x-4=7\\x-4=-7\end{matrix}\right.\)\(\Leftrightarrow\)\(\left[{}\begin{matrix}x=11\\x=-3\end{matrix}\right.\)
Vậy S={-3;11}
\(\sqrt{x^2-8x+16}=7\Leftrightarrow\sqrt{\left(x-4\right)^2}=7\)
\(\Leftrightarrow\left|x-4\right|=7\Leftrightarrow x-4=\pm7\)
\(\Leftrightarrow\left[{}\begin{matrix}x-4=7\\x-4=-7\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=11\\x=-3\end{matrix}\right.\)
Vậy, ...