If $$3x+y+k=0$$ is a tangent to the circle $$x^2+y^2=10$$, the values of k are

The equation to two circles which touch the Y-axis at (0, 3) and make an intercept of 8 units on X-axis are

$${x^2} + {y^2} - 6x - 6y + 4 = 0$$, $${x^2} + {y^2} - 2x - 4y + 3 = 0$$, $${x^2} + {y^2} + 2kx + 2y + 1 = 0$$. If the radical centre of the above three circles exists, then which of the following cannot be the value of k?

If the circles $${x^2} + {y^2} - 2x - 2y - 7 = 0$$ and $${x^2} + {y^2} + 4x + 2y + k = 0$$ cut orthogonally, then the length of the common chord of the circles is