Newton method , student need help.

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Thierry Gelinas
Thierry Gelinas 2015-4-10
评论： Torsten 2023-11-22
Hi , I know there's a lot of subjects on this but I didn't find what I'm looking for... This is my problem: I have create this code and it works perfectly well :
fonc=inline('fonction');
dfonc=inline('derivée de la fonction');
x=0.8;
;xn=0;
eps=1e-6;
k=0;
fprintf(' k x_k f(x_k) \n');
fprintf('%4d %12.4e %12.4e \n',k, x,fonc(x));
k=k+1;
while abs(x-xn) > eps & k < 20
xn=x;
x=x-fonc(x)/dfonc(x);
fprintf('%4d %12.4e %12.4e \n',k, x,fonc(x));
k=k+1;
end
In this case fonction = x^4-1.3*x^3-2.97*x^2+5.929*x-2.662 and dérivée de la fonction is 4*x^3-3.9*x^2-5.94*x+5.929
k x_k f(x_k)
0 8.0000e-01 -7.5600e-02
1 9.0370e-01 -2.1963e-02
2 9.7064e-01 -6.4300e-03
3 1.0144e+00 -1.8908e-03
4 1.0432e+00 -5.5753e-04
5 1.0623e+00 -1.6467e-04
6 1.0749e+00 -4.8691e-05
7 1.0833e+00 -1.4407e-05
8 1.0889e+00 -4.2649e-06
9 1.0926e+00 -1.2629e-06
10 1.0951e+00 -3.7405e-07
...
29 1.1000e+00 0.0000e+00
My problem is that I have to add a new thing to the table that would be create by this fonction:
abs((xn2-xn)/(xn-x)) and I don't know how to do it... I really need help.
It should be looking like this
k x_k f(x_k) |En+1/En|
0 8.0000e-01 -7.5600e-02 0,645515911
1 9.0370e-01 -2.1963e-02 0,653719749
2 9.7064e-01 -6.4300e-03 0,658135283
3 1.0144e+00 -1.8908e-03 0,663194444
4 1.0432e+00 -5.5753e-04 0,659685864
5 1.0623e+00 -1.6467e-04 ...
6 1.0749e+00 -4.8691e-05 ...
7 1.0833e+00 -1.4407e-05 ...
8 1.0889e+00 -4.2649e-06 ...
9 1.0926e+00 -1.2629e-06 ...
10 1.0951e+00 -3.7405e-07 ...
11 1.0967e+00 -1.1080e-07 ...
Thank you. ( by the way , english is not my native language so I'm sorry for all the mistakes I may have made. )

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回答（1 个）

Dendani
Dendani 2023-11-22
i need the solution of this fonction méthode of newton and secante X^2-7y+5 X^3+6x^2-xy+4
  1 个评论
Torsten
Torsten 2023-11-22
You have a system of 2 equations in 2 unknowns.
I've never heard that the secant method is used for systems of equations.
If you don't succeed or you are not keen on programming Newton's method on your own, I suggest a google search " MATLAB & Newton's method". There should be a lot of hits.

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