Exact values of the complex rational roots of a polynomial : crationalroot

### 2.29.4 Exact values of the complex rational roots of a polynomial : `crationalroot`

`crationalroot` takes 1 or 3 arguments : a polynomial and optionnally 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]`