Omg guys they did fanart of me!! kinda off tho- but its the thought that counts

that's

  2 units

Step-by-step explanation:

Completing the squares for the x- and y-terms, we get ...

  (x^2 + 8x) +(y^2 -6y) = -21

  (x^2 +8x +16) +(y^2 -6y +9) = -21 +16 +9

  (x +4)^2 +(y -3)^2 = 2^2

Compare this to the standard form equation for a circle:

  (x -h)^2 +(y -k)^2 = r^2

and we see that the radius (r) is 2.