Answer:
[tex] {x}^{2} + {y}^{2} = 81[/tex]
Step-by-step explanation:
The general for for the equation of a circle is
[tex] {(x - a)}^{2} + {(y - b)}^{2} = {r}^{2} [/tex]
Where a is the x coordinate of the centre, b is the y coordinate of the centre and r is the radius.
In your case, a=0, b=0, r=9
Substituting these values into the general form gives the answer.
