### 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 (x2+4)*(2x−3)=2*x3−3*x2+8*x−12, input :

crationalroot(2*x`^`3-3*x`^`2+8*x-12)

Output :

[2*i,3/2,-2*i]