please!數學高手！

The equation of family of circle which passes through the intersections of the two circles:

x2 + y2 + 2x - 4y - 4 + k(x2 + y2 - 4) = 0

(1 + k)x2 + (1 + k)y2 + 2x - 4y - 4(1 + k) = 0

x2 + y2 + 2/(1 + k) x - 4/(1 + k) y - 4 = 0

k is not equal to -1

Radius of the circle, r

= 1/2 sqrt{[2/(1 + k)]2 + [-4/(1 + k)]2 - 4(-4)}

= 1/(1 + k) sqrt[5 + 4(1 + k)2]

= 1/(1 + k) sqrt(9 + 8k + 4k2)

Area of the circle = 9π

So, πr2 = 9π

r = 3

1/(1 + k) sqrt(9 + 8k + 4k2) = 3

9 + 8k + 4k2 = 9 + 18k + 9k2

5k2 + 10k = 0

k = -2 or 0

For k = 0, it is exactly the circle x2 + y2 + 2x - 4y - 4 = 0

For k = -2, the equation of the circle:

x2 + y2 - 2x + 4y - 4 = 0