Snapping to Intercept Points & Extreme Points
f(x)=Polynomial({A,B,C,D,E})
list1=Join({{Extremum(f)},{Root(f)},{(0,f(0))}})
P'=Point(f)
Q=ClosestPoint(list1,P')
d=AxisStepX()/20
P=DynamicCoordinates(P',
If(Distance(P',Q)
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