We have the next polynomial function
In order to find the zero we punt the function equal to zero
We have a given zero that is 1-i
x=1-i
than means that we need the conjugate of the zero given is also a zero
x=1+i
and then we need a third zero because the polynomial has third-degree it can be calculated if we factorize the polynomial given
Therefore the zeros are
x=-1
x=1-i
x=1+i