The graph shows where the roots meet the x-axis. The Argand diagram shows where they go when they leave it.
The same two roots on an Argand diagram
Coefficients
a — shape and direction · b — sideways shift · c — up and down
Sliders step in whole numbers — type a decimal into a box if you need one.
Try these
Drag c slowly to move the curve through all three cases in turn.
The working