The radius of the circle is 9units and the center of the circle is at (5, 0)
Equation of a circle
The standard equation of a circle is expressed as:
(x-a)^2+(y-b)^2 = r^2
where
r is the radius of the circle
(a, b) is the centre of the circle
GIven the equation is (x – 5)² + y² = 81.
Compare both equations
a = 5, b = 0
r^2 = 81
r = 9units
Hence the radius of the circle is 9units and the center of the circle is at (5, 0)
Learn more on equation of circle here: https://brainly.com/question/14150470
