The following is one of literally thousands of interactive demonstrations in the Wolfram Demonstrations web site. You will need the free CDF player to run the demonstration. A small collection of these can be posted on a class web site for students to explore and then answer questions interactively, perhaps using Google forms, or as a hand-in assignment. Formulating good questions to go along with these demonstartions is a necessity if students are to comprehend the concepts. Otherwise, it may just seem to them like a dumbed down video game!
Quadratic in Vertex Form (or Turning Point Form) from the Wolfram Demonstrations Project by Rod Bate