Let (h, k) be the centre of a circle with radius a.
Thus, its equation will be .
(i) Given:
(x − 1)2 + y2 = 4
Here, h = 1, k = 0 and a = 2
Thus, the centre is (1, 0) and the radius is 2.
(ii) Given:
(x + 5)2 + (y + 1)2 = 9
Here, h = −5, k = −1 and radius = 3
Thus, the centre is (−5, −1) and the radius is 3.
(iii) Given:
The given equation can be rewritten as follows:
Thus, the centre is (2, −3).
And, radius =
(iv) Given:
The given equation can be rewritten as follows:
Thus, the centre is and and the radius is .