The equation of the circle which touches the circle ${x^2} + {y^2} - 6x + 6y + 17 = 0$ externally and to which the lines ${x^2} - 3xy - 3x + 9y = 0$ are normals, is
${x^2} + {y^2} - 6x - 2y - 1 = 0$
${x^2} + {y^2} + 6x + 2y + 1 = 0$
${x^2} + {y^2} - 6x - 6y + 1 = 0$
${x^2} + {y^2} - 6x - 2y + 1 = 0$
The number of common tangents to the circles ${x^2} + {y^2} = 1$and ${x^2} + {y^2} - 4x + 3 = 0$ is
The circles ${x^2} + {y^2} = 9$ and ${x^2} + {y^2} - 12y + 27 = 0$ touch each other. The equation of their common tangent is
The points of intersection of circles ${x^2} + {y^2} = 2ax$ and ${x^2} + {y^2} = 2by$ are
The equation of radical axis of the circles $2{x^2} + 2{y^2} - 7x = 0$ and ${x^2} + {y^2} - 4y - 7 = 0$ is
The number of common tangents to the circles ${x^2} + {y^2} = 4$ and ${x^2} + {y^2} - 6x - 8y = 24$ is