where is the problem

% Resoulision des systèmes non-linéaire 
clc
clear 
x1=5;
x2=5;
x3=5;
X=[x1;x2;x3];
deltx=1;
k=1;
while abs(deltx)>10^-6
    f=[3*X(1)+cos(X(2)*X(3))-1;X(1)^2-81*(X(2)+0.1)^2+sin(X(3))+0.25;exp(-X(1)*X(2))+20*X(3)+9];
    j=[3 -X(3)*sin(X(2)*X(3)) -X(2)*sin(X(2)*X(3));2*X(1) -162*(X(2)+0.1) cos(X(3));-X(2)*exp(-X(1)*X(2)) -X(1)*exp(-X(1)*X(2)) 20];
    deltx=-inv(j)*f;
    X=X+deltx;
    k=k+1;
end
format long
racinx1=X(1);
racinx2=X(2);
racinx3=X(3);

[John D'Errico]

Where is what problem? Does the code not run? Does it result in an error? Does it not do what you want it to do? (If so, then you need to tell people what you think it should be doing.)

[Walter Roberson]

deltx=1;

So it's a scalar?

    deltx=-inv(j)*f;

j is 3 x 3. f is 3 x 1. So inv(j)*f is 3 x 3 * 3 x 1, which is going to give a 3 x 1 result. So after that line, deltx is going to be 3 x 1, not a scalar.

while abs(deltx)>10^-6

Remember that for the purpose of if and while there is an implicit all() so the test is

while all(abs(deltx)>10^-6)

Is that what you want? Or do you want

while any(abs(deltx)>10^-6)

[belal hariz belgacem]

Thank you

The program works

My fault here ..........while abs(deltx)>10^-6

After correction

while all (abs(deltx)>10^-6)

[Walter Roberson]

Those would be the same thing to MATLAB, it automatically supplies all()