A. x2+y2-2x-4y+5=0

B. x2+y2-8x-6y+25=0

C. x2+y2-5x-5y+10=0

D. x2+y2+5x+5y-10=0

If the lines 2x+3y+1=0, 3x+2y-1=0 intersect the coordinate axes in four concyclic points then the equation of the circle passing through these four points is

If the circles x^{2}+y^{2}=3a^{2 }, x^{2}+y^{2}-6x-8y+9=0 touch externally then a=

The equation to the circles whose radius is 3 and which touches internally the circle x^{2}+y^{2}-4x+6y-12=0 at he point (-1, 1) is

The equation of the chord of contact of the point (4, 2) with respect to the circle x^{2}+y^{2}-5x+4y-3=0 is

The two circles x^{2}+y^{2}=a^{2}, x^{2}+y^{2}=c^{2}(c>0) touch each other if