Option d: 3 with multiplicity 4 and –6 with multiplicity 2
Step-by-step explanation:
The function is

To determine the roots of a polynomial, let us substitute
in the function

Thus, we have,

Thus, we have,

First solving the expression
, we have,
with multiplicity 4.
Also, solving the expression
, we have,
with multiplicity 2.
Thus, the roots of the polynomial function is 3 with multiplicity 4 and –6 with multiplicity 2
Hence, Option d is the correct answer.