### 5.27.20 Coefficients of a polynomial defined by its roots : pcoeff pcoef

pcoeff (or pcoef) takes as argument a list of
the roots of a polynomial P.

pcoeff (or pcoef) returns a univariate polynomial having
these roots,
represented as the list of its coefficients by decreasing order.

Input :

pcoef([1,2,0,0,3])

Output :

[1,-6,11,-6,0,0]

i.e. (x−1)(x−2)(x^{2})(x−3)=x^{5}−6x^{4}+11x^{3}−6x^{2}.