So, the formula for a diameter is D=2r
r=radius
D=diameter
It gives you a point, (-4,-2), so with this point you know that the radius is a little larger than -4 but you do not know the exact measurement, you can then use the x value, -4 and plug it into the formula, but we know that the radius is not going to be negative but instead positive
D=2(4)
D=8
As this is not the exact diameter but the closest to it is 8.94 so we can see that the actual radius is 8.94/2. Hope that makes sense,
Radius in this case is the distance from the origin to the edge of the circle.