Hey, me again.

The centres A,B, and C of the three circles are collinear. (A is smallest circle, B is biggest, C is 2nd biggest)

The equation of circle A is: (x + 12)² + (y + 15)² = 25

The equation of circle C is: (x - 24)² + (y - 12)² = 100

Find the equation of circle B.

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I done the easy part of finding the radius of Circle B (15). The bit i'm stuck at is finding the centre of circle B, which from the answer is(4,-3). Thanks

The answer is:x² + y² - 8x + 4y + 200 = 0