A. only I is true

B. only II is true

C. both I and II are true

D. neither I nor II true

If the circles x^{2}+y^{2}+2ax+4ay-3a^{2}=0 and x^{2}+y^{2}-8ax-6ay+7a^{2}=0 touch each other externally, the point of contact is

The equation of the circle whose centre lies in the first quadrant and which touches the coordinate axes and the line (x/3)+(y/4)=1 is x^{2}+y^{2}-2cx-2cy+c^{2}=0, then c=

The equation to the locus of the midpoints of chords of the circle x2+y2-8x+6y+20=0 which are parallel to 3x + 4y+5 = 0 is

The radical centre of the circle x^{2}+y^{2}=1, x^{2}+y^{2}-2x=1, x^{2}+y^{2}-2y=1 is

The length of the common chord of the circles x^{2}+y^{2}+2hx=0, x^{2}+y^{2}-2ky=0 is