Question

I need help with 3&4 ...

Answer 1

2*5=10 is the answer

Answer 2

General form for circle is 
(x - a)^2 + (y - b)^2 = r^2

so if center is at (3,-2) we can plug in a and b:-

(x-3)^2 + (y+2)^2 = r^2

Now plug in x = 7 and y =1  (from the point R)

4^2 + 3^2 = r^2 
r^2 =  25  making r = 5

so its diameter = 2*5 = 10