Question

Find the radius and centre of the circle $x^2+y^2-24y+128=0$.

Answer 1

Given the equation of the circle is $x^2+y^2-24y+128=0$

$x^2+y^2-24y+144=16$

or, $x^2+(y-12{)}^2=4^2$.

From this equation it is clear that the centre is $(0,12)$ and radius is $4$ units.