Answer: a. Radius of circle = 
b. The equation of this circle :
Step-by-step explanation:
Given : Center of the circle = (3,10)
Circle is passing through (12,12).
a. To find the radius we apply distance formula (∵ Radius is the distance from center to any point ion the circle.)
Radius of circle = 
Radius of circle = 
i.e. Radius of circle = 
b. Equation of a circle =
, where (h,k)=Center and r=radius of the circle.
Put the values of (h,k)= (3,10) and r=
, we get
∴ The equation of this circle :
Answer:

Step-by-step explanation:

hope this helps you.
Answer:
Option D.
Step-by-step explanation:
Consider option D. 
Take point (0,0)
On putting this point in inequation
, we get
which is true . So, solution is region towards the origin i,e region below the line
including the line itself .
On putting (0,0) in inequation
, we get
which is false , so solution is region away from the origin i.e region below line
including the line itself .
So, common solution to both the inequations is the shaded part in the given figure .
In other words, we can say that the graph shown in the given figure represents system of equations: 