## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

The equation $y=-{{x}^{2}}$.
The equation is equivalent to $y=-{{\left( x-0 \right)}^{2}}+0$. Now choose some value of x on both sides of the vertex and compute the corresponding y value. $\begin{matrix} x & y \\ 0 & 0 \\ 1 & -1 \\ 2 & -4 \\ -1 &-1 \\ -2 & -4 \\ \end{matrix}$ Now plot all the values of x and y on the rectangular coordinate system and join each point with one another to form a parabola. It can be concluded that the graph opens down because the coefficient of ${{x}^{2}}$ is negative