Answer:
12
Explanation:
The equation of a circle with center in (h, k) and radius r has the form
(x - h)² + (y - k)² = r²
In this case, the given equation is
x² + y² - 144 = 0
We can add 144 to both sides to get
x² + y² - 144 + 144 = 0 + 144
x² + y² = 144
Then, 144 = 12², so
x² + y² = 12²
Therefore, the radius of the circle is 12.
