How do you find the center and the radius of the circle whose equation is #x^2+y^2-4x-2y-4=0#?
centre = (2 , 1 ) and radius = 3
comparing the general form for the equation of a circle :
with the question given
# x^2 + y^2- 4x -2y - 4 = 0
comparing terms we can see that 2g = - 4 hence g = - 2
similarly 2f = - 2 hence f = - 1 and c = - 4
the centre of the circle = (- g , - f ) = (2 , 1 ) and