x*2+8x+16=7

x*2+8x+16=7   subtract 7 from both sides

x^2 + 8x + 9 = 0   this won't factor  ... using the on-site solver, we have

$${{\mathtt{x}}}^{{\mathtt{2}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{8}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,\small\textbf+\,}}{\mathtt{9}} = {\mathtt{0}} \Rightarrow \left\{ \begin{array}{l}{\mathtt{x}} = {\mathtt{\,-\,}}{\sqrt{{\mathtt{7}}}}{\mathtt{\,-\,}}{\mathtt{4}}\\
{\mathtt{x}} = {\sqrt{{\mathtt{7}}}}{\mathtt{\,-\,}}{\mathtt{4}}\\
\end{array} \right\} \Rightarrow \left\{ \begin{array}{l}{\mathtt{x}} = -{\mathtt{6.645\: \!751\: \!311\: \!064\: \!590\: \!6}}\\
{\mathtt{x}} = -{\mathtt{1.354\: \!248\: \!688\: \!935\: \!409\: \!4}}\\
\end{array} \right\}$$