5.30.4 Exact values of the complex rational roots of a polynomial : crationalroot
crationalroot takes 1 or 3 arguments : a polynomial and
optionally two complex numbers α,β.

If crationalroot has 1 argument, crationalroot returns the
list of the complex rational roots of the
polynomial without multiplicity.
 if crationalroot has 3 arguments, crationalroot returns only
the complex rational roots of the
polynomial which are in the rectangle with sides parallel to the
axis having [α,β] as opposite vertices.
To find the rational complex roots of
(x^{2}+4)*(2x−3)=2*x^{3}−3*x^{2}+8*x−12, input :
crationalroot(2*x^
33*x^
2+8*x12)
Output :
[2*i,3/2,2*i]