Add 5 to both sides: $\displaystyle{{\left({x}+{2}\right)}}^{{2}}={12}\usepackage{cmbright}\Huge\$

Use the Square Root Property: $\displaystyle{x}+{2}=\pm\sqrt{{12}}\usepackage{cmbright}\Huge\$

Subtract 2 from both sides: $\displaystyle{x}=-{2}\pm\sqrt{{12}}\usepackage{cmbright}\Huge\$

Simplify the radical: $\displaystyle{x}=-{2}\pm\sqrt{{{4}\cdot{3}}}=-{2}\pm{2}\sqrt{{3}}\usepackage{cmbright}\Huge\$