Questions in circle

Select	Question
	The equation of the circle touching $x=0,y=0$ and $x=4$ is
	The equation ${{x}^{2}}+{{y}^{2}}=0$ denotes
	$a{{x}^{2}}+2{{y}^{2}}+2bxy+2x-y+c=0$ represents a circle through the origin, if
	Equation of a circle whose centre is origin and radius is equal to the distance between the lines $x=1$ and $x=-1$ is
	A circle touches the axes at the points (3, 0) and (0, –3). The centre of the circle is
	If the centre of a circle is (2, 3) and a tangent is $x+y=1$ , then the equation of this circle is
	A circle which passes through origin and cuts intercepts on axes a and b, the equation of circle is
	A circle ${{x}^{2}}+{{y}^{2}}+2gx+2fy+c=0$ passing through $(4,\ -2)$ is concentric to the circle ${{x}^{2}}+{{y}^{2}}-2x+4y+20=0$ , then the value of c will be
	If the equation ${{x}^{2}}+{{y}^{2}}+2gx+2fy+c=0$ represents a circle with x-axis as a diameter and radius a, then
	The equation of a diameter of circle ${{x}^{2}}+{{y}^{2}}-6x+2y=0$ passing through origin is