Question

If -3+i is a root of the polynomial function f(x), which of the following must be a root of f(x)?

Answer 1

Use the conjugate of the 1st solution to find the second. which is -3 - i. or a

Answer 2

When dealing with imaginary numbers as roots of a polynomial, you will see that they always occur in conjugates. So the other root that goes with this one is -3 - i.  This will always be the case.