Correct. Rewrite the left side so that it is the square of a binomial: $\displaystyle{{\left({x}+{3}\right)}}^{{2}}={16}\usepackage{cmbright}\Huge\$

Take the square root of both sides: $\displaystyle{x}+{3}=\pm{4}\usepackage{cmbright}\Huge\$

Solve for x: $\displaystyle{x}=-{3}\pm{4}\usepackage{cmbright}\Huge\$

So $\displaystyle{x}=-{3}+{4}={1}\usepackage{cmbright}\Huge\$ or $\displaystyle{x}=-{3}-{4}=-{7}\usepackage{cmbright}\Huge\$