The equation $x^2 + y^2 = 0$ denotes

Find the area of the circle given by the equation $(x+1)(x+2)+(y-1)(y+3)=0$.

The equation of a circle of radius $5$ units touching another circle $x^2+y^2-2x-4y-20=0$ at $(5,5)$ is

If the lines $x + 2y - 5 = 0$ and $3x - y - 1 = 0$ denote two diameters of a circle of radius $5 \text{ units}$,then the equation of the circle is

$A$ point which lies on the circle passing through the points $(1,1), (-6,0),$ and $(-2,2)$ is

The equation of a circle touching the coordinate axes and the line $3x - 4y = 12$ is