Adding 4 from outside the radical means the graph will move four up from the graph of $\displaystyle\sqrt{{x}}\usepackage{cmbright}\Huge\$ . The graph of $\displaystyle{f{{\left({x}\right)}}}\usepackage{cmbright}\Huge\$ will begin at $\displaystyle{\left({0},{4}\right)}\usepackage{cmbright}\Huge\$ and increase, as does this graph. Check further by evaluating the function for different inputs. The graph must pass through $\displaystyle{\left({1},{5}\right)}\usepackage{cmbright}\Huge\$ , $\displaystyle{\left({4},{6}\right)}\usepackage{cmbright}\Huge\$ , and $\displaystyle{\left({9},{7}\right)}\usepackage{cmbright}\Huge\$ , and it does.