Maximum and Minimum Value of Quadratic Expression
For a > 0, the quadratic expression has a minimum value at x = -b/2a
For a < 0, the quadratic expression has a maximum value at x = -b/2a
x = -b/2a is the x-coordinate of the vertex of the parabola
For a > 0, Range: [f(-b/2a), ∞)
For a < 0, Range: (-∞, f(-b/2a)]