Answer:
center: (-1,0) ; radius: 9
Step-by-step explanation:
we know that
The equation of a circle in center radius form is equal to
[tex](x-h)^2+(y-k)^2=r^2[/tex]
where
(h,k) is the center of the circle
r is the radius of the circle
In this problem we have
[tex](x+1)^2+y^2=81[/tex]
so
The center (h,k) is the point [tex](-1,0)[/tex]
and
the radius
[tex]r^2=81\\r=9\ units[/tex]
therefore
center: (-1,0) ; radius: 9
