Module 7

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Horner's rule

An algorithm for the efficient evaluation of real-valued polynomials


In numerical mathematics, for the efficient evaluation of a real-valued polynomial pn(x) the Horner's rule (HR) is employed which is based on the identity

pn ( x ) = a 0 x n + a 1 x n-1 + a 2 x n-2 + ... + a n-2 x 2 + a n-1 x + a n
=((...(( a 0 x + a 1 ) x + a 2 ) x   + ... + a n-2 ) x + a n-1 ) x + a n .
(1)
(2)

7.1.

Explain, in how far this scheme constitutes an algorithm (compliance with the intuitive notion of an algorithm, presence of all characteristic features of an algorithm). Base your arguments on a representation of the HR using an appropriate notation as e.g. structograms (cf. [1]), decision tables, ... .

7.2.

Using the notation choosen previously, extend the algorithm HR to evaluate simultaneously with pn(x).


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