Respuesta :

[tex]\bf \textit{equation of a circle}\\\\ (x- h)^2+(y- k)^2= r^2 \qquad center~~\stackrel{origin}{(\stackrel{0}{ h},\stackrel{0}{ k})}\qquad \qquad radius=\stackrel{15}{ r} \\\\\\ (x-0)^2+(y-0)^2=15^2\implies x^2+y^2=225[/tex]