Function Description
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	Name: CUBIC 
	Function: f(x) = a*x*x*x + b*x*x + c*x + d
	Parameters: a b c d

Notes
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	Polynomial Fit to a cubic function
	This function converges with almost any starting parameters.

C-code for the function
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	answer = a*x*x*x + b*x*x + c*x + d;