$${\left({\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{1}}\right)}^{{\mathtt{2}}} = {{\mathtt{x}}}^{{\mathtt{2}}}{\mathtt{\,-\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,\small\textbf+\,}}{\mathtt{1}}$$
if you write your equation as this:$${\left({\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{1}}\right)}^{{\mathtt{2}}}{\mathtt{\,-\,}}{\mathtt{9}}$$
you can use this rule:$${{\mathtt{a}}}^{{\mathtt{2}}}{\mathtt{\,-\,}}{{\mathtt{b}}}^{{\mathtt{2}}} = \left({\mathtt{a}}{\mathtt{\,-\,}}{\mathtt{b}}\right){\mathtt{\,\times\,}}\left({\mathtt{a}}{\mathtt{\,\small\textbf+\,}}{\mathtt{b}}\right)$$
finally you can write your equation as:$$\left(\left({\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{4}}\right){\mathtt{\,\times\,}}\left({\mathtt{x}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2}}\right)\right)$$
so this means: 4 and -2 are your solutions. I hope I could explain
