Salut,

Qu'est-ce que c'est matlab?
Merci

Will

Bonjour Willw,

Mathlab est un programme informatique permettant de faire des mathématiques (en gros ).

A plus

yep Wilw, comme Mupad et Maple.

macho t'as pas une doc de Mathlab ?

Ok merci, je connaissais Maple. Ça existe sur mac?

Will

PS: "Ça existe sur mac?": je parlais de mathlab…

Merci

Will

salut macho,

sous matlab, c'est la fonction roots.
Je te copie l'aide sur la fonction

Syntax
r = roots(c)

Description
r = roots(c) returns a column vector whose elements are the roots of the polynomial c. Row vector c contains the coefficients of a polynomial, ordered in descending powers. If c has n+1 components, the polynomial it represents is . RemarksNote the relationship of this function to p = poly(r), which returns a row vector whose elements are the coefficients of the polynomial. For vectors, roots and poly are inverse functions of each other, up to ordering, scaling, and roundoff error.

Examples
The polynomial  is represented in MATLAB as p = [1 -6 -72 -27]
The roots of this polynomial are returned in a column vector by r = roots(p)

r =
    12.1229
    -5.7345
    -0.3884

Algorithm
The algorithm simply involves computing the eigenvalues of the companion matrix:
A = diag(ones(n-1,1),-1);
A(1,: ) = -c(2:n+1)./c(1);
eig(A)

It is possible to prove that the results produced are the exact eigenvalues of a matrix within roundoff error of the companion matrix A, but this does not mean that they are the exact roots of a polynomial with coefficients within roundoff error of those in c.

Remarque : je viens d'essayer qq exemples, en cas de racines multiples, il te la donne plusieurs fois, et il te donne les racines complexes.

Ptitjean