Answer:
8
Step-by-step explanation:
To write the equation of a circle, use the formula [tex](x-h)^2+(y-k)^2 = r^2[/tex] where the center of the circle is (h, k).
This means the equation is [tex]x^2 + y^2 = 64[/tex] has [tex]r^2 = 64[/tex]. This means the radius is √64 = 8.
