function apolloniusCircle(x1, y1, r1, x2, y2, r2, x3, y3, r3) {
const a2 = 2 * (x1 - x2),
b2 = 2 * (y1 - y2),
c2 = 2 * (r2 - r1),
d2 = x1 * x1 + y1 * y1 - r1 * r1 - x2 * x2 - y2 * y2 + r2 * r2,
a3 = 2 * (x1 - x3),
b3 = 2 * (y1 - y3),
c3 = 2 * (r3 - r1),
d3 = x1 * x1 + y1 * y1 - r1 * r1 - x3 * x3 - y3 * y3 + r3 * r3;
const ab = a3 * b2 - a2 * b3,
xa = (b2 * d3 - b3 * d2) / ab - x1,
xb = (b3 * c2 - b2 * c3) / ab;
const ya = (a3 * d2 - a2 * d3) / ab - y1,
yb = (a2 * c3 - a3 * c2) / ab;
const A = xb * xb + yb * yb - 1,
B = 2 * (xa * xb + ya * yb + r1),
C = xa * xa + ya * ya - r1 * r1,
r = A ? (-B - Math.sqrt(B * B - 4 * A * C)) / (2 * A) : (-C / B);
return {x: xa + xb * r + x1, y: ya + yb * r + y1, r};
}