You confused the graph of $\displaystyle{f{{\left({x}\right)}}}={3}-\sqrt{{{x}}}\usepackage{cmbright}\Huge\$ (shown in this answer) with the graph of $\displaystyle{f{{\left({x}\right)}}}=\sqrt{{{x}-{3}}}\usepackage{cmbright}\Huge\$ . Subtracting 3 on the inside of the radical moves the graph to the right. Adding 3 on the outside moves the graph up from the graph of $\displaystyle-\sqrt{{x}}\usepackage{cmbright}\Huge\$ .