how to solve this? i dont know how to find the centre

(x - a)^2 + (y - b)^2 = r^2
(-6 - a)^2 + (-2 - b)^2 = r^2
(3 - a)^2 + (1 - b)^2 = r^2

(-6 - a)^2 + (-2 - b)^2 = (3 - a)^2 + (1 - b)^2
(-6 - a)^2 - (3 - a)^2 + (-2 - b)^2 - (1 - b)^2 = 0
(-6 - a + 3 - a)(- 6 - a - 3 + a) + (-2 - b + 1 - b)(-2 - b - 1 + b) = 0
(-3 - 2a)(-9) + (-1 - 2b)(-3) = 0
27 + 18a + 3 + 6b = 0
18a + 6b + 30 = 0
3a + b + 5 = 0

Misal, (a, b) terletak di y = 2x - 10, maka :
b = 2a - 10

3a + b + 5 = 0
3a + 2a - 10 + 5 = 0
5a - 5 = 0
5a = 5
a = 1

b = 2(1) - 10
b = 2 - 10
b = -8

Jadi, titik pusatnya = (1, -8)


===

(x - a)^2 + (y - b)^2 = r^2
(3 - 1)^2 + (1 - (-8))^2 = r^2
2^2 + 9^2 = r^2
4 + 81 = r^2
r^2 = 85

Maka, persamaan lingkarannya adalah :
(x - 1)^2 + (y - (-8))^2 = r^2
x^2 - 2x + 1 + y^2 + 18y + 64 = 85
x^2 + y^2 - 2x + 18y - 20 = 0

===

refleksi terhadap garis x = -1
x' = x
y' = 2(-1) - y = -2 - y

(x - 1)^2 + (y - (-8))^2 = r^2
(x - 1)^2 + (-2 - y + 8)^2 = 85
(x - 1)^2 + (6 - y)^2 = 85
x^2 - 2x + 1 + 36 - 12y + y^2 = 85
x^2 + y^2 - 2x - 12y - 48 = 0