Answer:
The radius is 2 units.
Step-by-step explanation:
x^2 + y^2 + 8x − 6y + 21 = 0
Convert this to the general form (x - a)^2 + (y - b)^2 = r^2 by completing the square:
We have:
x^2 + 8x + y^2 - 6y = -21
(x + 4)^2 - 16 + (y - 3)^2 - 9 = -21
(x + 4)^2 + (y - 3)^2 = 4
Comparing with the above general form we see that
r^2 = 4
and therefore r = 2.
