You have to factor and then get the x intercepts
 
        
        
        
Answer:

Step-by-step explanation:
General Equation of circle is
 ----------- (1)
----------- (1)
Here

Radius r is distance from origin (x1, y1) to point (x2, y2)=(-3, -6)




Substituting values in equation (1)


 
        
             
        
        
        
Answer:
B because the rotation of the wheel doesn't change the angle of the spokes.
 
        
             
        
        
        
The answer is C. 
You need you use Pythagoras theorem 2 times to have 2 equations with the same sides i.e. for example a2 + b2 = 81 and a2 - b2 = 9. 
You can do it as you have different triangles but with the same sides.