You may have correctly rewritten the equation as $\displaystyle{{x}}^{{2}}+{8}{x}+{16}={27}\usepackage{cmbright}\Huge\$ , but made a mistake when factoring. The left side of this equation can be rewritten as $\displaystyle{{\left({x}+{4}\right)}}^{{2}}\usepackage{cmbright}\Huge\$ . You also need to simplify the radical.