When $\displaystyle{x}={0}\usepackage{cmbright}\Huge\$ in this equation, $\displaystyle{y}\usepackage{cmbright}\Huge\$ is also equal to zero, which means that the vertex would rest on the origin. In the graph, however, the vertex is at $\displaystyle{\left({0},-{4}\right)}\usepackage{cmbright}\Huge\$ .