4:14 , 6:21, 8:28, 10:35!!!
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
Answer:
b
Step-by-step explanation:
Hi there!
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I believe your answer is:

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Here’s why:
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Hope this helps you. I apologize if it’s incorrect.
Answer: 138
Step-by-step explanation: