A parabola has a vertex at (-1, 0) and opens down. What is the equation of the parabola?

The vertex form: y = a (x - h) ² + k

(h; k) the coordinates of vertex

(-1; 0) ⇒ h = - 1 and k = 0

therefore y = a (x + 1) ²

A parabola opens down, therefore a < 0.

Answer: y = a (x + 1) ² where a < 0.