Varying a
The animation shows how the graph of y = ax3 + bx2 + cx + d changes as a varies.

Varying b
The animation shows how the graph of y = ax3 + bx2 + cx + d changes as b varies.

What is the locus of the two turning points?
Varying c
The animation shows how the graph of y = ax3 + bx2 + cx + d changes as c varies.
