The vertex of parabola or a quadratic equation is the lowest or highest point of that equation.
Y = aX2 + bX + c (a≠0)
Then Vertex X Coordinate = -b/2a, Y coordinate = f(-b/2a).
For example, In a parabola or aquadratic equation like y = x2 + 2x + 5, x = -b/2a = -2 / 2*1 = -1/1 = -1. plug it back into the equation, y = 1 - 2 + 5 = 4, So the vertex of the parabola is (-1,4).