Questions in circle

Select	Question
	Give the number of common tangents to circle ${{x}^{2}}+{{y}^{2}}+2x+8y-23=0$ and ${{x}^{2}}+{{y}^{2}}-4x-10y+9=0$
	The number of common tangents to the circles ${{x}^{2}}+{{y}^{2}}=1$ and ${{x}^{2}}+{{y}^{2}}-4x+3=0$ is
	If line $ax+by=0$ touches ${{x}^{2}}+{{y}^{2}}+2x+4y=0$ and is a normal to the circle ${{x}^{2}}+{{y}^{2}}-4x+2y-3=0$ , then value of (a,b) will be
	If the equation of the tangent to the circle ${{x}^{2}}+{{y}^{2}}-2x+6y-6=0$ parallel to $3x-4y+7=0$ is $3x-4y+k=0$ , then the values of k are
	The locus of a point which moves so that the ratio of the length of the tangents to the circles ${{x}^{2}}+{{y}^{2}}+4x+3=0$ and ${{x}^{2}}+{{y}^{2}}-6x+5=0$ is $2:3$ is
	The common chord of the circle ${{x}^{2}}+{{y}^{2}}+4x+1=0$ and ${{x}^{2}}+{{y}^{2}}+6x+2y+3=0$ is
	If the middle point of a chord of the circle ${{x}^{2}}+{{y}^{2}}+x-y-1=0$ be (1, 1), then the length of the chord is
	$y=mx$ is a chord of a circle of radius a and the diameter of the circle lies along x-axis and one end of this chord in origin .The equation of the circle described on this chord as diameter is
	The locus of the middle points of those chords of the circle ${{x}^{2}}+{{y}^{2}}=4$ which subtend a right angle at the origin is
	The equation of the chord of the circle ${{x}^{2}}+{{y}^{2}}={{a}^{2}}$ having $({{x}_{1}},{{y}_{1}})$ as its mid-point is