\[x^{2} - 6x + 9 = 16\]
\[(x - 3)^{2} = 4^{2}\]
\[x - 3 = 4\]
\[x = 7;\]
\[x - 3 = - 4\]
\[x = - 1.\]
\[Ответ:\ - 1;7.\]