A. x2+y2-x-2y=0

B. x2+y2=4

C. x2+y2+4=0

D. none

If the two circle x^{2}+y^{2}+2gx+c=0 and x^{2}+y^{2}-2fy-c=0 have equal radius then locus of (g, f) is

The point (3, -4) lies on both the circles x^{2}+y^{2}-2x+8y+13=0 and x^{2}+y^{2}-4x+6+11=0. Then the angle between the circles is

The nearest point on the circle x^{2}+y^{2}-6x-4y-12=0 from (-5, 4) is

The equation of the tangents to a circle x^{2}+y^{2}-4x-6y-12=0 and parallel to 4x-3y=1 are

The equation of the chord of the circle x^{2}+y^{2}=25 with (1, -1) as the midpoint is