The normal at a point $$P$$ on the ellipse $${x^2} + 4{y^2} = 16$$ meets the $$x$$- axis $$Q$$. If $$M$$ is the mid point of the line segment $$PQ$$, then the locus of $$M$$ intersects the latus rectums of the given ellipse at the points

The centres of two circles $${C_1}$$ and $${C_2}$$ each of unit radius are at a distance of 6 units from each other. Let P be the mid point of the line segement joining the centres of $${C_1}$$ and $${C_2}$$ and C a circle touching circles $${C_1}$$ and $${C_2}$$ externally. If a common tangent to $${C_1}$$ and passing through P is also a common tangent to $${C_2}$$ and C, then the radius of the circle C is

The smallest value of $$k$$, for which both the roots of the equation $$${x^2} - 8kx + 16\left( {{k^2} - k + 1} \right) = 0$$$ are real, distinct and have values at least 4, is