Incorrect. Starting with $\displaystyle{4}\pi{{r}}^{{2}}={A}\usepackage{cmbright}\Huge\$ , solve for r by first dividing both sides of the equation by $\displaystyle{4}\pi\usepackage{cmbright}\Huge\$ , then taking the square root of both sides of the equation. Remember that $\displaystyle\sqrt{{{{r}}^{{2}}}}={r}\usepackage{cmbright}\Huge\$ since r represents the radius, which is positive.