Question

Find the center and the radius of the circle given by x^2+8x+y^2-69-24=0

The answer I got is center = (4,0) and radius = sq rt 109 ... but others tell me center (-4,0) and radius sq rt 77 which one is right answer?

Answer 1

The others are right:

For an equation of circle:

\[\large{x^2 + y^2 + 2gx + 2fy + c = 0}\]

\[\large{\text{centre} = (-g,-f)}\]

\[\large{\text{radius} = \sqrt{g^2 + f^2 -c}}\]

Answer 2

Thank you for the help.

Answer 3

No problem :)