You have a lot of questions here, I can help you with a few of them.
When you simplify the polynomials, you put together all of the terms that have the same degree. That means the variables have the same exponents. The number of terms are the items separated by plus and minus signs.
Here are the answers for the first three:
1)

2)

3)
Answer:
8.6
Step-by-step explanation:
a^2+b^2=c^2
7^2+5^2=c^2
49+25=c^2
74=c^2
8.6=c
Answer:
c
Step-by-step explanation:
i just did the test this is my first answer please like
1)B two real roots.
2)D two complex roots.
3) and 4) later