Find a polynomial of degree 3 with the following zeros 1, -3+i

Which sum or difference identity would you use to verify that cos (180° - ∅) = -cos ∅? a. sin (α -β) = sin α cos β – cos α sin β b. cos (α -β) = cos α cos β – sin α sin β c. cos (α -β) = cos α cos β + sin α sin β d. sin (α + β) = sin α cos β + cos α sin β

Precalculus question, image attached.

Asequence is a function whose is the set of natural numbers