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

Let the abscissae of the two points $P$ and $Q$ be the roots of $2x^{2}-rx+p=0$ and the ordinates of $P$ and $Q$ be the roots of $y^{2}-sy-q=0$. If the equation of the circle described on $PQ$ as diameter is $2(x^{2}+y^{2})-11x-14y-22=0$,then $2r+s-2q+p$ is equal to

Find the equation of a circle that touches the lines $x = 0$,$y = 0$,and $x = 2c$.

Find the equation of the circle which passes through the points $(2, -2)$ and $(3, 4)$ and whose centre lies on the line $x + y = 2$.

Which of the following is the equation of a circle?

Find the equation of the circumcircle of the triangle formed by the lines $x = 0$,$y = 0$,and $\frac{x}{a} - \frac{y}{b} = 1$.