COMPANION _ _ _ _ _ _ _ _ _ _ _ _ operator
<poly> :- a monic univariate polynomial in <x>.
<x> :- the variable.
companioncreates the companion matrix C of <poly>.
This is the square matrix of dimension n, where n is the degree of <poly> w.r.t. <x>.
The entries of C are:
C(i,n) = -coeffn(<poly>,<x>,i-1) for i = 1 ... n, C(i,i-1) = 1 for i = 2 ... n and the rest are 0.
companion(x^4+17*x^3-9*x^2+11,x); [0 0 0 -11] [ ] [1 0 0 0 ] [ ] [0 1 0 9 ] [ ] [0 0 1 -17]
Related functions: find_companion.