What is the quadratic formula in vertex form?

See explanation below to use the vertex form to solve a quadratic equation.

Step-by-step explanation:

(x - h) ^2 - k = 0, the vertex is (h, - k)

An example below, taking a quadratic equation and completing the square:

x^2 - 2x - 1 = 0

x^2 - 2x = 1

(-2/-2) ^2 = 1, add 1 to both sides of the equation.

x^2 - 2x + 1 = 1 + 1

(x - 1) ^2 = 2

(x - 1) ^2 - 2 = 0

The vertex is (1, - 2)