By definition we have to:
A set has under an operation if performance of that operation on set members always produces a member of the same set; in this case we also say that the set is closed under the operation.
For this case we have the following polynomials:

Multiplying we have:

The product of two polynomials is also a polynomial.
Answer:
d
is a polynomial
Sorry i didn’t understood the question
Answer:
C
Step-by-step explanation:
Yes, ACD = BCD by AAS since they have 2 congruent angles & share a side.
8. It is a function, the x’s do not repeat
9. It is not a function, -3 is listed twice
So you would do
5×4×3= 60
and
5×4=20
so, for a 3 digit code there are 60 possibilities and for a 2 digit code there are 20 possibilities.