Answer: A. (-1,-10)
The x-coordinate of the vertex can be calculated using [tex]x=-\frac{b}{2a}[/tex].
According to the equation given a = 1, and b = 2.
[tex]x=-\frac{b}{2a} =-\frac{2}{2(1)}=-\frac{2}{2} =-1[/tex]
The y-coordinate of the vertex can be calculated by subbing in the x-value from the previous equation (x = -1) for x, and solving for y.
[tex]y=x^{2}+2x-9=(-1)^{2}+2(-1)-9=1-2-9=-10[/tex]
∴ the vertex is (-1,-10).
