Using basic algebra, as shown below, we can prove that the product of two linear functions gives a quadratic function. This property is explored interactively using an applet.
Two links related to the study of the properties of quadratic functions are shown below.

Let h and g be two linear functions of the form
where a and A are non zero constants. It can easily be shown that the product of functions h and g is a quadratic function. Let f be the function obtained as the product of g and h as follows: f(x) = (h · g) (x) = h(x) · g(x) = ( a x + b ) · ( A x + B ) = a A x^{ 2} + (a B + b A) x + b B An applet below may be used to explore the properties of the quadratic function f obtained above by changing the parameters a, b , A and B included in the definition of the two linear functions. There are other tutorials you may want to work through later: tutorials on quadratic functions and graphing quadratic functions.
A  Quadratic Functions From Linear Functions : Interactive TutorialThe button below starts the applet on a separate large screen.
Continue to Page 1 (quadratic Functions  General form)
Derivatives of Quadratic Functions: Explore the quadratic function f(x) = ax ^{ 2} + b x + c and its derivative graphically and analytically. Find Vertex and Intercepts of Quadratic Functions  Calculator: An applet to solve calculate the vertex and x and y intercepts of the graph of a quadratic function. Tutorial on Quadratic Functions (1). Quadratic Functions  Problems (1). graphing quadratic functions . quadratic functions in vertex form . 