Prove that the centres of the three circles {x^2} + {y^2} - 4x - 6y - 12 = 0{x^2} + {y^2} + 2x + 4y - 5 = 0 and  {x^2} + {y^2} - 10x - 16y + 7 = 0 are collinear.
Prove that the centres of the three circles {x^2} + {y^2} - 4x - 6y - 12 = 0{x^2} + {y^2} + 2x + 4y - 5 = 0 and  {x^2} + {y^2} - 10x - 16y + 7 = 0 are collinear.

Answer:

Given,

x2 + y2 – 4x – 6y – 12 = 0

Centre ( – g1, – f1) = (2, 3)

x2 + y2 + 2x + 4y – 5 = 0

Centre ( – g2, – f2) = ( – 1, – 2)

x2 + y2 – 10x – 16y + 7 = 0

Centre ( – g3, – f3) = (5, 8)

 

x1, y1 are the coordinates of the centre and so on.

 

=> 2( – 2 – 8) – 3( – 1 – 5) + 1( – 8 + 10)

=> – 20 + 18 + 2 = 0

 

 

 

 

 

The centres are collinear.