You may have thought that, because any real number can be substituted for x, both the domain and range are all real numbers. However, the graph of this function is a parabola. There will be a minimum value at the vertex of the parabola, which is the point $\displaystyle{\left({0},-{3}\right)}\usepackage{cmbright}\Huge\$ . The range of the function is therefore $\displaystyle{f{{\left({x}\right)}}}\ge-{3}\usepackage{cmbright}\Huge\$ .