Question

Find the centre & radius of the circle whose equation is x² + y² – 4x + 6y + 12 = 0.

Answer 1

Comparing it with the general equation x² + y² + 2gx + 2fy + c = 0, we have 

2g = – 4 ⇒ g = –2 

2f = 6 ⇒ f = 3 

& c = 12 

∴ centre is (–g, –f) i.e. (2, –3)