Question

1) What is the standard form of the equation of the circle in the graph?

Answer 1

First find the coordinate of the center:
(1,2)
Then find the value pf the radio, which is the distance 
from the center to the perimeter:
r = 4.
Given center (s,t) and radius r, the formula o the equation is the following 
$(x-s)^2+(y-t)^2=r^2$
We deduce the equation:
$(x-1)^2+(y-2)^2=16$