QUADRATIC FUNCTIONS
A function is quadratic if it has this algebraic expression: y = f(x) = ax2 + bx + c (a,b,c єR, a≠0), with a polynomial of degree 2.
Its graph is a parabola, with a relative extremum in a point called vertex of the parabola.
The vertex has x = -b/2a as abscissa, and the parabola has a symmetry axis in x = -b/2a.