Comparing the given equation x2+y2−16=0⇒x2+y2=16⇒x2+y2=42
with the general equation for the circle centered at origin i.e., x2+y2=r2,
we get, radius of the given circle, r = 4 units.
We are required to find centre and radius of a circle concentric to the given circle and with radius its double.
So, radius of the required circle will be 2×4=8 units.
And we know that concentric circles will have same centre which will be origin in this case. So, centre of the required circle = (0, 0).