Answer:
a) We get

So, Is the result of A+B is a polynomial:Yes
b) We get

So, Is the result of A-B is a polynomial:Yes
c) We get

So, Is the result of A.B is a polynomial:Yes
Explanation:
We are giving the polynomial equations:

We need to find
a) A+B

So, we get

So, Is the result of A+B is a polynomial:Yes
b) A-B

So, we get

So, Is the result of A-B is a polynomial:Yes
c) A . B

So, we get

So, Is the result of A.B is a polynomial:Yes