Answer:
A) 
Step-by-step explanation:
The equation of a circle is
where
is the center and
is the radius. If
and
, then:

Therefore, the equation of the circle is 
Answer:
square root(-1) = i
Step-by-step explanation:
D. 311 divided by 12 = 25.91
The nearest tenth would be 25.9
Answer: a^3+81ab^2
First, you square (a+9b) which will become (a^2+81b^2)
Then, you multiply it by a and you will get a^3+81ab^2