You correctly identified the domain of the function. However, you may not have graphed the function, or you missed that the square root of the function is multiplied by a negative number. Because $\displaystyle\sqrt{{{x}-{3}}}\ge{0}\usepackage{cmbright}\Huge\$ , it follows that $\displaystyle-\sqrt{{{x}-{3}}}\le{0}\usepackage{cmbright}\Huge\$ . Use this fact to find the range.