The parabola on the graph opens downward and its vertex is at the origin $\displaystyle{\left({0},{0}\right)}\usepackage{cmbright}\Huge\$ . Although the graph of this equation would face downward, the $\displaystyle+{4}\usepackage{cmbright}\Huge\$ causes the vertex of the parabola to be at $\displaystyle{\left({0},{4}\right)}\usepackage{cmbright}\Huge\$ .