Answer:
The circle equation is [tex]x^{2}+y^{2}=9[/tex]
Step-by-step explanation:
The rule of the equation of the circle whose center (h , k) and radius r is:
[tex](x-h)^{2}+(y-k)^{2}=r^{2}[/tex]
∵ The center of the circle is the origin (0 , 0) and its radius is 3
∴ The equation is [tex](x-0)^{2}+(y-0)^{2}=3^{2}[/tex]
∴ [tex]x^{2}+y^{2}=9[/tex]
