The axis of symmetry of this equation is at -1.
We can determine this in any equation in vertex form just by looking at it. Firstly, start with the base form of vertex form.
y = (x - h)^2 + k
In this equation (h, k) is the vertex. Working by this fact, we know the vertex is (-1, 0). The axis of symmetry is always the x value of the vertex, which allows us to state the vertex at x = -1.
