Question

Find the centre and the radius of the given circles:

1. (x-1)2 +(y+1)2 = 1
2. x2 +y2 = 4

Answer 1

The equation of the circle is (x-a)² + (y-b)² = R², where (a,b) - are the coordinates of the center, R - radius.
Thus
1. (1,-1) - the centre, R = 1
2. (0,0) - the centre, R = 2