If $5 x+6 y-34=0$ and $2 x+y+c=0$ are conjugate lines with respect to the circle $x^2+y^2-8 x-10 y+25=0$, then the point on the line $2 x+y+c=0$ is

If $C_1$ and $C_2$ are the centres of similitude with respect to the circles $x^2+y^2+6 x+8 y+24=0$ and $x^2+y^2-6 x-8 y+9=0$, then $C_1 C_2=$

Let $x+y=0$ be the radical axis of the circles $S \equiv x^2+y^2+2 g x+2 f y+c=0$ and $S \equiv x^2+y^2-6 x-4 y+4=0$ and the radius of the circle $S=0$ be 1 . The $g+f=$

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