The equation of the radical axis of the circles $x^2+y^2+4x+6y+7=0$ and $4x^2+4y^2+8x+12y-9=0$ is:

The radius of the circle which cuts all the three circles $x^2+y^2-4x-4y+3=0$,$x^2+y^2+4x-4y+3=0$,and $x^2+y^2+4x+4y+3=0$ orthogonally is

The equation of the family of circles passing through the point of intersection of a circle $S = 0$ and a line $P = 0$ is given by:

If the curves $x^{2}-6x+y^{2}+8=0$ and $x^{2}-8y+y^{2}+16-k=0$ $(k>0)$ touch each other at a point,then the largest value of $k$ is

The limiting points of the co-axial system containing the two circles $x^2+y^2+2x-2y+2=0$ and $25(x^2+y^2)-10x-80y+65=0$ are

The equation of the circle passing through the points of intersection of two circles $x^2+y^2+2x+3y+1=0$ and $x^2+y^2+4x+3y+2=0$ and the point $(-1,1)$ is