Example 4.  Use the Horner's method with vector coefficients to calculate [Graphics:Images/HornerMod_gr_127.gif] and [Graphics:Images/HornerMod_gr_128.gif] for the polynomial
        [Graphics:Images/HornerMod_gr_129.gif].  
Use these values to perform one step in Newton's method for approximating a root using the initial approximation  [Graphics:Images/HornerMod_gr_130.gif].  

Solution 4.

[Graphics:../Images/HornerMod_gr_131.gif]


[Graphics:../Images/HornerMod_gr_132.gif]

Use the recursive formulas to compute the sequence  [Graphics:../Images/HornerMod_gr_133.gif].  

[Graphics:../Images/HornerMod_gr_134.gif]



[Graphics:../Images/HornerMod_gr_135.gif]

Use the recursive formulas to compute the sequence  [Graphics:../Images/HornerMod_gr_136.gif].  

[Graphics:../Images/HornerMod_gr_137.gif]



[Graphics:../Images/HornerMod_gr_138.gif]

The coefficients [Graphics:../Images/HornerMod_gr_139.gif] and [Graphics:../Images/HornerMod_gr_140.gif] can be used with to perform one step of Newton iteration for finding a root starting with the initial guess  [Graphics:../Images/HornerMod_gr_141.gif] and using the Newton-Raphson formula:

    [Graphics:../Images/HornerMod_gr_142.gif].

[Graphics:../Images/HornerMod_gr_143.gif]



[Graphics:../Images/HornerMod_gr_144.gif]

We are done.

Aside.  We can check out the formulas

    [Graphics:../Images/HornerMod_gr_145.gif]
and
    [Graphics:../Images/HornerMod_gr_146.gif]

 

[Graphics:../Images/HornerMod_gr_147.gif]

[Graphics:../Images/HornerMod_gr_148.gif]


[Graphics:../Images/HornerMod_gr_149.gif]

[Graphics:../Images/HornerMod_gr_150.gif]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(c) John H. Mathews 2004