The equation of a circle is given as:
(x-a)^2 + (y- b)^2 = r^2 where (a, b) is the center.
(x-9)^2 = x^2 -18x + 81 - ----(i)
(y+2)^2 =y^2 + 4y +4 ------ (ii)
r^2 = 49 ------ (iii)
Adding equation (i) and (iii)
x^2 + y^2 - 18x + 4y + 85 -----(iv)
Equating equation (iv) and (iii)
x^2 + y^2 - 18x + 4y + 85 = 49
Arrange the equation:
x^2 + y^2 - 18x + 4y + 36 = 0
I hope this helps
