You have simplified $\displaystyle{\log}_{{{6}}}{{\left({6}{x}\right)}}^{{2}}\usepackage{cmbright}\Huge\$ as if it were $\displaystyle{\log}_{{{6}}}{6}{{x}}^{{2}}\usepackage{cmbright}\Huge\$ . The first step is to use the power property, $\displaystyle{\log}_{{{6}}}{{\left({6}{x}\right)}}^{{2}}={2}\cdot{\log}_{{{6}}}{6}{x}\usepackage{cmbright}\Huge\$ . You can rewrite further using the product property.