Questions in circle

Select	Question
	If circles ${{x}^{2}}+{{y}^{2}}+2ax+c=0$ and ${{x}^{2}}+{{y}^{2}}+2by+c=0$ touch each other, then
	If d is the distance between the centres of two circles, ${{r}_{1}},{{r}_{2}}$ are their radii and $d={{r}_{1}}+{{r}_{2}}$ , then
	The points of intersection of circles ${{x}^{2}}+{{y}^{2}}=2ax$ and ${{x}^{2}}+{{y}^{2}}=2by$ are
	A circle with radius 12 lies in the first quadrant and touches both the axes, another circle has its centre at (8,9) and radius 7. Which of the following statements is true
	The equation of radical axis of the circles ${{x}^{2}}+{{y}^{2}}+x-y+2=0$ and $3{{x}^{2}}+3{{y}^{2}}-4x-12=0,$ is
	If the centre of a circle which passing through the points of intersection of the circles ${{x}^{2}}+{{y}^{2}}-6x+2y+4=0$ and ${{x}^{2}}+{{y}^{2}}+2x-4y-6=0$ is on the line $y=x$ , then the equation of the circle is
	If the circles ${{x}^{2}}+{{y}^{2}}-2ax+c=0$ and ${{x}^{2}}+{{y}^{2}}+2by+2\lambda =0$ intersect orthogonally, then the value of $\lambda $ is
	The radical axis of the pair of circle ${{x}^{2}}+{{y}^{2}}=144$ and ${{x}^{2}}+{{y}^{2}}-15x+12y=0$ is
	The condition that the circle ${{(x-3)}^{2}}+{{(y-4)}^{2}}={{r}^{2}}$ lies entirely within the circle ${{x}^{2}}+{{y}^{2}}={{R}^{2}},$ is
	The value of $\lambda $ , for which the circle ${{x}^{2}}+{{y}^{2}}+2\lambda x+6y+1=0$ , intersects the circle ${{x}^{2}}+{{y}^{2}}+4x+2y=0$ orthogonally is