EDIT: Just found the solutions a few posts below me so ...
This is from Cambridge 4 unit:
Show that if the polynomials P<sub>1</sub>(z)=b<sub>n</sub>z<sup>n</sup> + b<sub>n-1</sub>z<sup>n-1</sup> + … + b<sub>0</sub> and P<sub>2</sub>(z)=c<sub>n</sub>z<sup>n</sup> + … + c<sub>0</sub> are...