how the distance between centre of circle if: x^2+y^2+2x-2y-11=0 and x^2+y^2-4x+6y-17=0

From the given circles:

C1 : x^2+y^2+2x-2y-11=0 and
C2 : x^2+y^2-4x+6y-17=0

Rewrite in the standard form:
C: (x-x1)^2+(y-y1)^2 = r^2
where (x1,y1) is the centre of the circle, and r the radius.

C1 : (x+1)^2 + (y-1)^2 = 9
C2 : (x-2)^2 + (y+3)^2 = 4
Find the centre of each circle and hence the distance between them.