The vertex form of a quadratic function, which is in the form f(x) = a(x-h)^2 + k, is the easiest form to use to find the maximum or minimum value of the function. This is because the vertex form immediately gives you the coordinates of the vertex, which is the maximum (if the coefficient of x^2 is negative) or minimum (if the coefficient of x^2 is positive) value of the function.
