ModNewt:

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   Finds the solution to f(x) = 0 given derivative information.
   Uses df(x)/dx when only one root is possible. If there are multiple
    roots, x should be in the vicinity of the desired root.

   Since version 1.
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   Form:
   [x, n] = ModNewt( f, fD, fDD, x, epsilon, nMax, varargin )
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   Inputs
   ------
   f                     String name of f(x),      i.e. 'f'
   fD                    String name of df(x)/dx   i.e. 'dfdx'
   fDD                   String name of d2f(x)/dx2 i.e. 'd2fdx2'
   x                     Initial guess
   epsilon               Tolerance
   nMax                  Max number of iterations (can be inf)
   varargin              Optional arguments

   -------
   Outputs
   -------
   x                     Result
   n                     Number of iterations

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	References:	Hornbeck, R., Numerical Methods, Quantum, 1975, pp. 69-70.
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