Multiplying the radical by a negative number changes the direction of the graph. Subtracting 3 outside the radical means the graph will move three down. The graph of $\displaystyle{f{{\left({x}\right)}}}\usepackage{cmbright}\Huge\$ will begin at $\displaystyle{\left({0},-{3}\right)}\usepackage{cmbright}\Huge\$ and decrease, as does this graph. Check further by evaluating the function for different inputs. The graph must pass through $\displaystyle{\left({1},-{4}\right)}\usepackage{cmbright}\Huge\$ , $\displaystyle{\left({4},-{5}\right)}\usepackage{cmbright}\Huge\$ , and $\displaystyle{\left({9},-{6}\right)}\usepackage{cmbright}\Huge\$ , and it does.