Question 724585
(x – 1)² + (y + 1)² = 4 

Compare it to

(x – h)² + (y - k)² = r²

x - 1 = x - h
    h = 1

y + 1 = y - k
    k = -1

So the center = (h,k) = (1,-1)

r² = 4
 r = 2

So the radius is 2. 

Edwimn</pre>