Function: polfromroots
Section: polynomials
C-Name: polfromroots
Prototype: GDn
Help: polfromroots(a,{v=x}): returns the monic polynomial in variable v
 whose roots are the components of the vector a with multiplicities.
Doc: returns the monic polynomial in variable \kbd{v} whose roots are the
 components of the vector $a$ with multiplicities, that is
 $\prod_{i} (x - a_{i})$.
 \bprog
 ? polfromroots([1,2,3])
 %1 = x^3 - 6*x^2 + 11*x - 6
 ? polfromroots([z, -z], 'y)
 %2 = y^2 - z^2
 @eprog
