she means equation addiii...
yeah It's
r=8cm....let centre be (h,k)
let point P be a point on the circumference of a circle with coordinates (x,y)
then
(x-h)2 + (y-k)2=r2
(x-h)2+(y-k)2=16(42)
I assume centre is (0,0) since it is not given
assuming....h and k become 0
x2+y2=16
equation is x2+y2-16=0